Keywords

Introduction

The virilizing congenital adrenal hyperplasias are a family of autosomal recessive disorders affecting adrenal steroidogenesis that are characterized by excessive adrenal androgen production. The most common form is 21-hydroxylase deficiency (21-OHD) due to mutations in the 21-hydroxylase (CYP21A2) gene. The other virilizing forms are 3β-hydroxysteroid dehydrogenase and 11β-hydroxylase deficiencies associated with mutations in the 3β-hydroxysteroid dehydrogenase (HSD3B2) and 11β-hydroxylase (CYP11B1) genes, respectively. Another form of CAH associated with genital ambiguity is oxidoreductase deficiency (PORD), which is associated with mutations in the cytochrome P450 oxidoreductase (POR) gene. POR encodes a flavoprotein that serves as an electron donor for cytochrome P450 steroidogenic enzymes such as 21-hydroxylase. Congenital lipoid adrenal hyperplasia (CLAH) is associated with mutations in the steroidogenic acute regulatory protein (StAR) gene, undervirilization of male fetuses, and absence of circulating steroid hormones. Mutations in 17α-hydroxylase/17,20-lyase (CYP17A1) are associated with undervirilization in males, absent puberty in females, and hypertension. Mutations in the aromatase (CYP19A1) gene interfere with the conversion of androgens to estrogens and are characterized by maternal virilization during puberty, virilization of female fetuses, failure of epiphyseal fusion, tall stature, and hyperandrogenic symptoms in adolescent and adult females. This chapter will focus on 21-hydroxylase deficiency because it is the most common form of congenital adrenal hyperplasia. A brief outline of other defects in steroidogenesis is provided in Table 5.1.

Table 5.1 Disorders of steroidogenesis . Gene, gene location, and typical phenotypes are listed. In general, severity of phenotype correlates with genotype
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The clinical features associated with CAH comprise a spectrum reflecting the consequences of the specific mutation. In the case of 21-OHD, the continuum ranges from salt-losing and simple virilizing forms to the milder forms. Collectively, the salt-losing and simple virilizing forms are considered to be the classic forms. The mild form is also known as the late-onset or nonclassic form (NCAH). This classification system is somewhat contrived because disease severity is better represented as a continuum based on residual enzyme activity. The incidence of the classic forms ranges from 1:5000 to 1:15,000 with variation among ethnic/racial backgrounds [1]. The prevalence of 21-OHD is lower among African-Americans than Caucasians in the United States [2]. Incomplete ascertainment muddies accurate determination of the incidence of NCAH. However, available data indicate that NCAH may occur in 1:1000 with increased frequency among Hispanics, Yugoslavs, and Ashkenazi Jews [3].

Pathophysiology

In these disorders, the loss of cortisol negative feedback inhibition leads to increased hypothalamic corticotrophin-releasing hormone (CRH) and pituitary adrenocorticotropic hormone (ACTH) secretion. The excessive ACTH secretion leads to accumulation of steroid hormone intermediates proximal to the deficient enzyme and hyperplasia of the zona fasciculata and zona reticularis.

In the classical pathway of adrenal steroidogenesis (Fig. 5.1), cholesterol is converted to pregnenolone by the P450 side-chain cleavage enzyme encoded by CYP11A1. Most steroidogenic enzymes are cytochrome P450 enzymes which acquired their family name because they absorb light at 450 nm when reduced with carbon monoxide [4]. In the zona glomerulosa, pregnenolone is converted to progesterone by 3β-hydroxysteroid dehydrogenase type 2 encoded by HSD3B2. Progesterone is converted to dexoxycorticosterone by 21-hydroxylase and subsequently to aldosterone by aldosterone synthase encoded by CYP11B2. Aldosterone secretion is regulated by the renin-angiotensin system and serum potassium concentrations.

Fig. 5.1
figure 1

Pathways of adrenal steroid hormone synthesis particularly relevant for 21-OHD. CYP11A1 cytochrome P450 cholesterol side-chain cleavage, StAR steroidogenic acute regulatory protein, CYP17A1 17α-hydroxylase/17,20-lyase, HSD3B2 3β-hydroxysteroid dehydrogenase type 2, P450oxido P450-oxidoreductase, CYB5A cytochrome b5, type A, SULT2A1 sulfotransferase 2A1, CYP21A2 21-hydroxylase, CYP11B1 11β-hydroxylase, CYP11B2 aldosterone synthase, AKR1C3 17β-hydroxysteroid dehydrogenase type 5, SRD5A 5α-reductase

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In the zona fasciculata, pregnenolone is hydroxylated by the enzyme 17α-hydroxylase/17,20-lyase encoded by CYP17A1 to 17-hydroxypregnenolone, which is converted to 17-hydroxyprogesterone (17-OHP) by 3β-hydroxysteroid dehydrogenase type 2. Subsequently, 17-OHP is converted by 21-hydroxylase to 11-deoxycortisol, which is then converted by 11β-hydroxylase to cortisol. In the zona reticularis, the enzyme 17α-hydroxylase/17,20-lyase converts 17-hydroxypregnenolone to dehydroepiandrosterone (DHEA), which is subsequently converted to androstenedione by 3β-hydroxysteroid dehydrogenase type 2. DHEA can undergo sulfation by steroid sulfotransferase, SULT2A1, to form DHEAS.

Thus, the substrates immediately proximal to 21-hydroxylase, progesterone and 17-OHP, are elevated in patients with 21-OHD. Unfortunately, the pathophysiology of CAH is more complex than would be predicted for an autosomal recessive disorder in which the expression of the defective protein is limited to the adrenal cortex. This complexity is likely due to genetic variants at other loci which influence steroid metabolism and steroid responsiveness. More recently described alternative pathways affecting steroid hormone metabolism may also influence the clinical manifestations.

In the alternative “backdoor” pathway, 17-OHP is sequentially converted by 5α-reductase and the 3α-reductase activities of AKR1C2/4 to generate 5α-pregnane-3α,17α-diol-20-one (pdiol) that is subsequently converted to dihydrotestosterone (DHT) [5]. This alternative pathway bypasses testosterone as an intermediate. Urinary concentrations of metabolites indicative of increased flux through the alternative pathway are higher in affected individuals, particularly infants [6]. This pathway may contribute to the androgen excess responsible for prenatal virilization of affected female fetuses [7].

Under normal circumstances, the direct conversion of 17-OHP to androstenedione is not significant in humans. Yet, when 17-OHP accumulates in 21-OHD, it is metabolized by this alternative pathway [8]. Defective 21-OHD also promotes accumulation of other steroid hormone intermediates such as 21-deoxycortisol, 16α-hydroxyprogesterone, 11-ketoandrostenedione, and 11-ketotestosterone [9]. The enzyme 17β-hydroxysteroid dehydrogenase type 5 also known as aldo-keto reductase 1C3 (AKR1C3) can convert DHEA and androstenedione to androstanediol and testosterone, respectively [10]. It has been suggested that 11β-hydroxyandrostenedione, 11-ketoandrostenedione, 11β-hydroxytestosterone, and 11-ketotestosterone (11KT) are specific markers for adrenal-derived C-19 androgen hormones [11]. Regarding androgenic potency, 11β-hydroxytestosterone and 11-ketotestosterone have similar but slightly lower androgenic activity than testosterone using an in vitro cell-based luciferase reporter assay [12].

Clinical Features

Consequences of cortisol deficiency include poor cardiac function, poor vascular response to catecholamines, and increased secretion of antidiuretic hormone [13]. For 21-OHD, complete loss of function mutations abrogate aldosterone synthesis leading to hyponatremia due to impaired urinary sodium reabsorption. The hyponatremia leads to hypovolemia, elevated plasma renin levels, and, eventually, shock if not promptly recognized and treated. In the absence of aldosterone, potassium cannot be excreted efficiently resulting in hyperkalemia [14]. In 21-OHD, the elevated 17-OHP and progesterone concentrations exacerbate the mineralocorticoid deficiency because both hormones have antimineralocorticoid effects and, in vitro, interfere with aldosterone-mediated mineralocorticoid receptor transactivation [15]. In addition, the lack of prenatal cortisol exposure disrupts adrenomedullary development and can be associated with epinephrine deficiency and hypoglycemia [16].

Female infants with classical 21-OHD, either salt-losing or simple virilizing, generally present in the neonatal period with ambiguous genitalia. In some instances, the diagnosis of genital ambiguity has been suspected based on prenatal ultrasound findings. For affected female infants, the external genital findings can range from a nearly male appearance with penile urethra and bilateral undescended testes to minimal clitoromegaly. The most common physical findings in affected girls include clitoromegaly, fused rugated labia majora, and a single perineal orifice. The extent of prenatal virilization can lead to misassignment of gender at birth. Occasionally, the minimally virilized girl may not be identified until progressive clitoromegaly prompts a medical evaluation.

Affected 46,XX female infants with 21-OHD have normal female internal genitalia. The uterus can be identified on ultrasound. The ovaries may be too small to be visualized on ultrasound. Despite excessive prenatal androgen exposure, ovarian position is normal, Mullerian structures persist, and the Wolffian ducts regress. The Mullerian structures develop normally to form the fallopian tubes, uterus, and upper vagina. Virilized girls may have incomplete separation of the urethra and vagina resulting in a urogenital sinus and a single perineal orifice.

Apart from hyperpigmentation, external genital development is normal in boys with 21-OHD. Whereas girls are usually detected due to genital ambiguity, boys with salt-losing CAH appear well in the immediate newborn period. Infants with CAH tend to feed poorly and fail to regain their birth weight. Typically, they develop vomiting, hypotension, hyponatremia, and hyperkalemia in the first 10–14 days of life. Prior to implementation of newborn screening, affected boys typically presented with hyponatremic dehydration, hyperkalemia, and shock with the potential for a fatal outcome.

Pubarche refers to the development of pubic hair, axillary hair, apocrine body odor, and acne. Pubarche is the physical manifestation of adrenarche which reflects adrenal pubertal maturation and increased production of adrenal C19 steroids. Children with simple virilizing or NCAH often present with premature development of pubic hair (premature pubarche). Premature pubarche is defined as the presence of pubic hair, axillary hair, or apocrine odor developing before 8 years in girls and 9 years in boys. Additional features in children include tall stature, accelerated linear growth velocity, and advanced skeletal maturation. Clitoromegaly may develop in girls. Boys manifest phallic enlargement with prepubertal-sized testes. In a multicenter study, children less than 10 years of age most often presented with premature pubarche [17]. Among children with premature pubarche, the diagnosis of CAH should be considered when basal 17-OHP, androstenedione, and testosterone concentrations are elevated and/or bone age is advanced [18]. Nevertheless, CAH is an uncommon cause of premature adrenarche [19].

Symptoms of milder, late-onset, or nonclassic 21-OHD (NC-21-OHD) include hirsutism, irregular menses, chronic anovulation, acne, and infertility. Hirsutism, defined as excessive growth of coarse terminal hairs in androgen-dependent areas in women, has been reported to be the most common presenting feature among women [20, 21]. Hirsutism reflects the apparent sensitivity of the pilosebaceous unit/hair follicle to both circulating androgen and local androgen concentrations. Importantly, the extent of the hirsutism correlates poorly with circulating androgen concentrations [22].

Acne can occur among patients with NC-21-OHD but is rarely the primary clinical manifestation. Consideration should be given to further evaluation for patients with severe cystic acne refractory to oral antibiotics and retinoic acid treatment. Severe androgenic alopecia accompanied by marked virilization in older previously undiagnosed women has been described [23].

The nature of the symptoms leads to an ascertainment bias favoring diagnosis in affected women. Men with NC-21-OHD are typically identified through family studies. Individuals with NC-21-OHD usually do not have elevated ACTH concentrations. Some have an overresponsive ACTH-stimulated glucocorticoid response, possibly reflective of subtle adrenal hyperplasia [24].

Due to the similar clinical features, it may be difficult to distinguish women with NC-21-OHD from those with polycystic ovary syndrome (PCOS) [25, 26]. Women with NC-21-OHD tend to have higher 17-OHP and progesterone concentrations than women with PCOS [27]. Insulin resistance, obesity, polycystic ovary morphology, and elevated LH/FSH ratios tend to be more common among women with PCOS. However, none of these features clearly differentiate women with NCAH from those with PCOS [28]. Anti-Mullerian hormone concentrations do not discriminate women with NCAH from those with PCOS [29].

Family studies have demonstrated that not all individuals with genotypes consistent with NC-21-OHD develop symptoms of androgen excess. Curiously, in a study of 145 probands with 21-OHD, 4% of parents were identified to have undiagnosed or cryptic NC-21-OHD [30]. Apart from infertility among the women, these individuals had achieved normal adult heights and did not report episodes of adrenal insufficiency [30].

One uncommon feature is an adrenal myelolipoma. These adrenal mass lesions consist of myeloid, erythroid, and megakaryocytic cell lines and appear as hyperechoic masses on ultrasound and fat-containing masses on CT scan. Typically, these lesions are benign, but larger lesions are at risk for hemorrhage or rupture. MRI signal characteristics depend on the composition of the lesion.

Hypothalamic-Pituitary-Gonadal (HPG) Axis and Reproductive Concerns

Oligo-amenorrhea , chronic anovulation , and infertility are common presenting complaints for women with NC-21-OHD and can occur in women with classic 21-OHD despite adequate hormone replacement therapy. Hence, women with 21-OHD can develop a secondary “PCOS” phenotype [31]. The specific molecular mechanisms responsible for the altered hypothalamic-pituitary-adrenal (HPO) axis function accompanied by apparent ovarian androgen excess are unclear. Increased circulating concentrations of adrenal androgens and progestins likely influence HPO axis function.

Additional features affecting female reproduction include vaginal stenosis with dyspareunia , impaired sensation , changes in cervical mucous, poor self-esteem, and disinterest in having children. Impaired quality of life and risk for depression have been reported to be higher in women with 21-OHD [32]. Potential contributing factors include engaging in high-risk behaviors, perception of being different from other women, and perceived lack of autonomy [33]. Reproductive outcomes for women with CAH can be greatly improved by adequate suppression of progesterone and 17-OHP to promote ovulation and implantation of the fertilized ovum; this may require optimizing both glucocorticoid and mineralocorticoid therapies [34]. Occurrence of miscarriages is higher among untreated women with NC-21-OHD [20, 21]. The consequences of prenatal androgen exposure on the developing female brain are being explored [35].

Quality of life (QoL) for women with CAH has been a long-standing concern for women with CAH. One series reported later sexual debut, fewer pregnancies and children, and increased incidence of homosexuality; these outcome measures were related to type of surgical correction and the severity of their mutations [36]. Girls with CAH are reported to prefer more masculine toys, more male-dominant occupations, rougher sports, and non-heterosexual orientation [37]. Another series of 24 women, who answered a questionnaire, reported that 87.5% of women indicated that CAH had not interfered with their social relationships [38]. Regarding gender identity and sexual orientation, 25% of women indicated that they had occasionally wished to be a man, and 62% reported having heterosexual orientation at all times [38]. This area of investigation has been confounded with several factors including small numbers of subjects, lack of control subjects, changes in surgical techniques over time, and variability of age at the time of surgical correction.

Careful consideration regarding surgery is urged for girls with genital ambiguity. Only experienced surgeons/urologists should perform feminizing genitoplasty and vaginal reconstruction [39]. During adolescence, the adequacy of the vaginal introitus for the use of tampons and sexual intercourse should be assessed. For girls with vaginal stenosis, dilatation is often helpful.

Gonadal adrenal rest tumors , predominantly testicular adrenal rests (TARTs) , occur in up to half of men with 21-OHD. These tumors arise from adrenal cells that descend with the testes during testicular development. TARTs are not malignant but can compress the rete testis and seminiferous tubules culminating in testicular atrophy and obstructive azoospermia. Ultrasound and MRI are helpful to detect TARTs less than 2 cm because small lesions are generally not palpable. TARTs may be present in childhood and adolescence and have rarely been described in men with NC-21-OHD [40, 41]. Although TARTs have been attributed to poor adherence with hormone replacement therapy, pathogenesis of TARTS may be more complicated [42]. In affected males, the elevated adrenal C19 steroid secretion can suppress gonadotropin secretion resulting in hypogonadotropic hypogonadism and subsequent oligospermia. Ovarian adrenal rest tumors (OARTs) have been infrequently reported in affected women.

Molecular Genetics

The CYP21A2 gene is located in a complex genetic region at chromosome 6p21.3 where it lies in close proximity to a highly homologous pseudogene, CYP21A1P. CYP21A2 and CYP21A1P are arranged in tandem repeats with the C4A and C4B genes, which encode complement component 4. The tenascin (TNX) and serine threonine nuclear protein kinase (RP) genes are also mapped to this region. These four genes, RP, C4, CYP21, and TNX, form a unit known as RCCX. Most alleles carry two RCCX units in which one has CYP21A2 and the other has CYP21A1P (Fig. 5.2

Fig. 5.2
figure 2

Genetic organization of CYP21A2 and CYP21A1P. This figure illustrates the location of the C4A, CYP21A2, C4B, and CYP21A1P genes on the short arm of chromosome 6

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).

To date, over 200 CYP21A2 mutations have been reported (http://www.hgmd.cf.ac.uk; www.cypalleles.ki.se). Yet, despite the large number of reported mutations, approximately ten mutations account for the majority of affected alleles. Most mutations result from gene conversion events in which the functional gene acquires deleterious CYP21A1P sequences or from misalignment during meiosis that can give rise to duplication or deletions of the RCCX unit. Haplotypes with three or four RCCX units have been described [43]. Another example of misalignment is a CYP21A1P/CYP21A2 chimera in which a portion of the CYP21A1P gene is fused to a portion of the CYP21A2 gene [44]. Rarely, CAH can be associated with uniparental disomy [45]. The de novo mutation rate is approximately 1%.

Most affected individuals are compound heterozygotes with different mutations on each allele. Mutations range from complete loss of function to mild missense mutations. Estimates of in vitro 21-hydroxylase activity range from <1% for mutations associated with salt-losing CAH to 2–10% for simple virilizing CAH and to 30–50% for NCAH. Genotype, residual enzyme activity, and phenotype generally correlate such that an individual’s phenotype reflects their milder mutation. Patients with classical salt-losing CAH usually carry complete loss of function mutations on both alleles. Patients with simple virilizing CAH typically have a complete loss of function mutation on one allele and the I172N or intron 2 splicing mutation on their other allele. Patients with NCAH often carry different mutations with at least one allele carrying a mild missense mutation such as V281 L. Approximately 25–50% of individuals with NCAH are reported to have mild mutations on both alleles [46,47,48]. Mutations associated with NCAH include V281L, P453S, and R339H. The P30L mutation is often detected in patients with NCAH but is typically associated with more severe androgen excess [49].

As noted above, the CYP21A2 locus is quite complex which precludes molecular genetic analysis as the first-line diagnostic test. Molecular genetic testing is also confounded by the possibility of multiple mutations on a single allele and the presence of different CYP21A2 mutations in one family. Multiple genetic testing strategies such as PCR-based mutation detection methods, sequencing, and multiplex ligation-dependent probe amplification may be needed to accurately interrogate and segregate the mutations in an affected individual. In some instances, it may be necessary to perform genetic analyses on the parents to segregate the specific maternal and paternal mutations and confirm that mutations are on opposite alleles. Despite these potential obstacles, genetic analysis can be a useful adjunct to newborn screening [50].

As noted above, one RCCX unit contains CYP21 and TNX genes (Fig. 5.2). TNXB encodes tenascin-X, which is an extracellular matrix glycoprotein involved in collagen organization and matrix integrity. Mutations in TNXB are associated with Ehlers-Danlos syndrome. Several distinct alleles have been characterized with loss of CYP21A2 and specific TNXB alleles. Patients have been described to have monoallelic or biallelic TNXB variants. The severity of the Ehlers-Danlos syndrome is dependent on the TNXB genotype. Patients with CAH will benefit from evaluation for features associated with Ehlers-Danlos syndrome such as hypermobile joints and skin laxity [51].

Diagnosis

An elevated 17-OHP concentration provides confirmation of the diagnosis of 21-OHD deficiency. Most affected infants have random 17-OHP values >5000 ng/dl (150 nmol/L) [52]. For infants, additional laboratory evaluation can include electrolytes, plasma renin activity, progesterone, and androstenedione concentrations. Pelvic ultrasound imaging and chromosome analyses are recommended for virilized female infants.

For individuals with symptoms suggestive of NC-21-OHD, an early morning basal 17-OHP has been suggested as an effective screening test. Armengaud et al. reported 100% sensitivity and 99% specificity with a threshold value of 200 ng/dl (6  nmol/L) to diagnose NC-21-OHD in children with premature pubarche [19]. A bone age X-ray should be obtained to assess for acceleration of skeletal maturation.

Blood samples for 17-OHP determinations should be obtained in the follicular phase for reproductive-aged cycling women because the 17-OHP concentration may be elevated during the luteal phase. In this situation, Escobar-Morreale et al. recommended using a basal 17-OHP of 170 ng/dl (5.1 nmol/L) as the “cut point” for women [53]. Nevertheless, for any age group, an ACTH stimulation test may be warranted to complete the evaluation for 21-OHD. For an ACTH stimulation test, following collection of a basal blood sample, 0.25 mg synthetic ACTH (Cortrosyn) is administered by intravenous or intramuscular routes; a second blood sample is collected at 30 and/or 60 min. In addition to 17-OHP, cortisol should be measured especially among individuals with NC-21-OHD to assess the adequacy of cortisol secretion. To differentiate 21-OHD from other disorders of steroidogenesis, determination of progesterone, 17-hydroxypregnenolone, 11-deoxycortisol, DHEA, deoxycorticosterone, and androstenedione may be warranted [54].

In general, CYP21A2 mutations on both alleles will be identified when ACTH-stimulated 17-OHP concentrations are greater than 1500 ng/dl (45 nmol/L). However, some individuals with diagnostic genotypes have ACTH-stimulated 17-OHP values between 1000 and 1400 ng/dl (30–45 nmol/L). Individuals with 21-OHD have elevated 21-deoxycortisol concentrations, but commercial availability of this hormone assay is limited. Liquid chromatography-tandem mass spectroscopy (LC-MS/MS) has demonstrated elevated 17-OHP, 21-deoxycortisol, 16α-hydroxyprogesterone, and progesterone; these steroids comprise sensitive and specific biomarkers to accurately identify patients with CAH due to 21OHD [9]. As noted above, the 11oxo-C19 steroids, 11β-hydroxyandrostenedione, 11-ketoandrostenedione, 11β-hydroxytestosterone, and 11-ketotestosterone (11KT), are elevated in 21-OHD [11].

Newborn Screening

Newborn screening (NBS) for 21-OHD was initiated in the late 1970s using filter paper whole-blood 17-OHP measurements of whole-blood 17-OHP [55]. All 50 states and many countries have developed NBS programs. To minimize false-positive results, blood samples should be collected after 48 h of life. Automated time-resolved dissociation-enhanced lanthanide fluoroimmunoassays (DELFIA) are often used for 17-OHP determinations. The major goals of NBS are to identify infants with salt-losing 21-OHD, to prevent misidentification of affected females, and to decrease the morbidity and mortality associated with acute adrenal insufficiency [56]. Nevertheless, false-positive screening results occur among preterm, stressed, or heterozygous infants. Cross-reactivity with sulfated steroids and 16α-hydroxyprogesterone is another reason for false-positive results. Decreased 11β-hydroxylase activity in the neonate may be another confounder contributing to false-positive testing [57]. Birth weight and gestational age cut points have been developed to minimize recalls for false-positive tests. False-negative 17-OHP results leading to delayed diagnoses have been reported for both newborn girls and boys [58].

Treatment

Treatment needs to be focused on the individual’s symptoms. In other words, treatment should not be initiated merely to decrease abnormally elevated hormone concentrations. For children and adolescents, treatment goals include normal linear growth velocity, normal rate of skeletal maturation, appropriately timed spontaneous pubertal development, and positive self-esteem. Treatment goals for adolescent and adult women include normal menstrual cyclicity, fertility, and prevention of further hirsutism and acne. Maintenance of fertility is also a concern for adult males with classic CAH. Healthcare should ideally be provided in a multidisciplinary setting with endocrinologists, pediatricians/internists, surgeons/urologists/gynecologists, behavioral health specialists, and nurse educators [59].

Laboratory goals include androstene dione and testosterone concentrations that are appropriate for age, gender, and stage of puberty. Normalization of 17-OHP and progesterone concentrations generally indicates excessive hormone replacement therapy.

Hydrocortisone (Cortef®) is the preferred glucocorticoid replacement in infants, children, and adolescents. The usual dosage ranges from 6 to 15 mg/m2/day generally administered three times per day (for a 1.75 m2 individual, 7.5 mg in the morning, 5 mg in the afternoon, and 10 mg before bed are equivalent to 12.8 mg/m2/day). Some clinicians advocate reverse circadian dosing with the highest dose in the evening. However, the larger bedtime dose may not adequately suppress the early morning ACTH rise, and some individuals complain of insomnia with a higher bedtime dose. Hydrocortisone dose equivalence greater than 17 mg/m2/day during childhood (> 30 mg per day for a 1.75 m2 individual) was associated with greater compromise of adult height [60]. Prednisone and dexamethasone have longer half-lives such that less frequent dosing is needed; these medications may be considered for use in the adult patient. Some adult patients with classic CAH are well controlled on combinations of hydrocortisone and small doses of prednisone or dexamethasone at bedtime [61]. Some women with CAH experience persistent hyperandrogenic anovulation and benefit from taking oral contraceptives. Cosmetic hair removal including shaving, waxing, electrolysis, laser therapies, and topical eflornithine cream may be helpful.

Several factors should be contemplated regarding the use of glucocorticoid replacement therapy for patients with NC-21-OHD. Many patients with NC-21-OHD will not require daily glucocorticoid replacement to maintain their health. Indeed, the vast majority of men with NC-21-OHD are generally asymptomatic and do not benefit from treatment. Older adolescent and adult women can be treated with oral contraceptives to decrease the ovarian contribution to androgen excess. Children and adolescents with NC-21-OHD may have extremely advanced skeletal maturation and may benefit from glucocorticoid replacement therapy. For patients with NC-21-OHD, daily or stress-dose glucocorticoid treatment may be indicated only when ACTH-stimulated cortisol is less than 18 mg/dl (500 nmol/L). Some women and men with NC-21-OHD may benefit from short-term hydrocortisone or prednisolone therapy to treat infertility [62]. As noted above, suppression of progesterone can improve fecundity in women with CAH [34]. Hence, therapy for patients with NC-21-OHD needs to be individualized and may vary according to the patient’s specific current needs.

The synthetic hormone, 9α-fludrocortisone acetate, is used for mineralocorticoid replacement with the goal of achieving a plasma renin activity that is within normal limits for age. Due to their salt-poor diet, transient pseudohypoaldosteronism, and immature kidneys, infants typically require higher mineralocorticoid replacement during the first few months of life. Some infants may require additional salt supplementation.

Stress dosing is necessary for significant illnesses, surgery, or life-threatening stress. Tripling the usual daily dose is the semi-arbitrary guideline for stress dosing. If the individual is unable to take or tolerate oral medications, parental hydrocortisone should be administered as follows: < 12 months of age, 25 mg; 1–4 years of age, 50 mg; and > 4 years of age, 100 mg. All individuals on glucocorticoid treatment require instruction regarding oral stress doses and administration of parental hydrocortisone. All patients with CAH should wear medical alert identification badges/jewelry.

Treatment of CAH is often challenging because of the difficulty inherent in balancing overtreatment and undertreatment. Parameters that influence optimal dosing include variation in absorption from the gastrointestinal tract, CBG concentrations, and cortisol half-life in the circulation [63]. For this reason, novel th erapies are being explored. One approach has been the development of a time-released glucocorticoid preparation, Chronocort® [64]. Continuous glucocorticoid replacement using a subcutaneous pump has been tried [65]. In a short clinical trial, abiraterone acetate, which inhibits CYP17A1, has been used in conjunction with replacement hydrocortisone treatment [66].

Prenatal Treatment

To prevent prenatal virilization of the external genitalia of affected females, prenatal dexamethasone treatment was explored starting in the 1980s [67, 68]. Dexamethasone has been used because it is not inactivated by 11β-hydroxysteroid dehydrogenase type 2 and can cross the placenta. Whereas this treatment appears to be efficacious to decrease virilization of the external genitalia, numerous safety concerns have arisen. To be effective, dexamethasone treatment must be started within 6–7 weeks of conception. Yet, genetic diagnosis by chorionic villus biopsy cannot be safely done until 10–12 weeks. Thus, all at-risk pregnancies are treated even though only one in eight fetuses is predicted to be an affected female and seven of eight fetuses are unnecessarily exposed to prenatal dexamethasone treatment.

Clinical outcome studies have demonstrated increased social anxiety, low birth weight (LBW), failure to thrive, developmental delay, mood disturbance, and poor school performance. Hirvikoski et al. reported a significant negative effect on short-term memory/verbal working memory in children unaffected with CAH who had been treated with dexamethasone during the first trimester of fetal life; however, long-term memory and learning, as well as full-scale IQ, were comparable to untreated controls [69]. Early prenatal dexamethasone exposure has been reported to affect cognitive functions in healthy unaffected girls [70].

In another treatment paradigm, antenatal GCs are used in infants at risk for preterm delivery. In this situation, structural changes in the brain characterized by cortical thinning specifically in the rostral anterior cingulate cortex in children 6–10 years of age were reported in term infants. This area of the brain is important for emotional regulation [71].

Data available in additional clinical outcome studies and using animal models raise significant concern about the use of prenatal dexamethasone and urge that it not be used except in research studies under the guidance of the appropriate Institutional Review Board [72]. One novel approach has utilized cell-free DNA that is found in the maternal circulation. Identification of the SRY gene accompanied by sequencing of the CYP21A2 gene has been used to identify affected females who might benefit from treatment [73]. The drawback of this approach is that the results must be quickly obtained to guide treatment decisions. Another option is preimplantation genetic diagnosis, which allows selection of unaffected embryos for reimplantation [74].

Outcome

Data reporting outcome on older populations of patients with CAH are disappointing. Treatment regimens vary widely with use of diverse glucocorticoid preparations, differing dosages, and dissimilar regimens regarding diurnal dosing. Medical issues identified in adults in the CaHASE study from the United Kingdom included osteopenia, osteoporosis, short stature, obesity, hypertension, and infertility [75, 76]. Data accrued through the NIH Natural History Study showed poor outcomes associated with highly variable treatment attributed to generally poor adherence to medical management [77]. Bachelot et al. reported their outcome experience regarding adult patients followed at a single medical center; they found obesity, abnormal bone mineral density, adrenal tumors, TARTs, and menstrual irregularity were common [78]. Analysis of patients with CAH enrolled in the Swedish CAH register revealed increased cardiovascular and metabolic morbidity especially obesity [79]. The common theme for these disappointing outcome studies is poor medical supervision and suboptimal management in adult patients. Patients seem to be lost for follow-up after transitioning from pediatric to adult healthcare.

Future Directions

In the interval of time since the initial description of CAH by Luigi de Crecchio, much has been learned about the pathophysiology and molecular genetics of this common autosomal recessive disorder [80]. Nevertheless, better diagnostic tools and improved hormone replacement regimens would greatly benefit our patients [81]. Finally, as more 21OHD patients are adults than children, the focus of research needs to shift to transition of care, long-term complications, and reproductive health.