Abstract
Background: The causes of subclinical hyperthyroidism have only been reported from clinical studies. Aim: To determine the prevalence and pathological causes of reduced serum TSH levels in subjects recruited from an epidemiological survey. Material/subjects and methods: Serum TSH was measured in 7954 subjects in the 5th Tromsø study. Subjects with serum TSH<0.50 mlU/l, not using T4, without a previous diagnosis of thyroid disease, without serious concomitant disease, and younger than 80 yr, were invited for a re-examination. If low serum TSH was persistent,thyroid scintigraphy was performed. Results: Among the 4962 subjects that met the inclusion criteria, serum TSH was <0.50 mlU/l in 105 subjects. Twelve subjects had a suppressed serum TSH level (<0.05 mlU/l). Two of these were lost to follow-up, 4 had Graves’ disease, 4 had adenoma, and 2 had multinodular goiter. In the 93 subjects with serum TSH 0.05–0.5 mlU/l, 55 were re-examined, of whom 35 had normalized their serum TSH level. In the remaining 20 subjects, 1 had Graves’ disease, 6 had adenoma (of which 2 were toxic adenomas), 7 had multinodular goiter, and 6 were considered normal. Among the 521 subjects using T4, 70 (13.4%) had a suppressed serum TSH level. Conclusions: Most of the subjects with a suppressed serum TSH level will be on T4 medication. Otherwise, if the suppressed serum TSH level is found by chance, this probably represents a clinically important thyroid pathology. Also, in subjects with a persistently low serum TSH level (0.05–0.5 mlU/l) most will have a pathological thyroid scan.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Cooper DS. Hyperthyroidism. Lancet 2003, 362: 459–68.
Surks MI, Ortiz E, Daniels GH, et al. Subclinical thyroid disease: scientific review and guidelines for diagnosis and management. JAMA 2004, 291: 228–38.
Sawin CT, Geller A, Wolf PA, et al. Low serum thyrotropin concentrations as a risk factor for atrial fibrillation in older persons. N Engl J Med 1994, 331: 1249–52.
Kalmijn S, Mehta KM, Pols HA, Hofman A, Drexhage HA, Breteler MM. Subclinical hyperthyroidism and the risk of dementia. The Rotterdam study. Clin Endocrinol (Oxf) 2000, 53: 733–7.
Biondi B, Palmieri EA, Fazio S, et al. Endogenous subclinical hyperthyroidism affects quality of life and cardiac morphology and function in young and middle-aged patients. J Clin Endocrinol Metab 2000, 85: 4701–5.
Parle JV, Maisonneuve P, Sheppard MC, Boyle P, Franklyn JA. Prediction of all-cause and cardiovascular mortality in elderly people from one low serum thyrotropin result: a 10-year cohort study. Lancet 2001, 358: 861–5.
Førde OH, Thelle DS. The Tromsø heart study: risk factors for coronary heart disease related to the occurrence of myocardial infarction in first degree relatives. Am J Epidemiol 1977, 105: 192–9.
Jorde R, Saleh F, Figenschau Y, Kamycheva E, Haug E, Sundsfjord J. Serum parathyroid hormone (PTH) levels in smokers and non-smokers. The fifth Tromsø study. Eur J Endocrinol 2005, 152: 39–45.
Intenzo CM, dePapp AE, Jabbour S, Miller JL, Kim SM, Capuzzi DM. Scintigraphic manifestations of thyrotoxicosis. Radiographics 2003, 23: 857–69.
Tollin SR, Fallon EF, Mikhail M, Goldstein H, Yung E. The utility of thyroid nuclear imaging and other studies in the detection and treatment of underlying thyroid abnormalities in patients with endogenous subclinical thyrotoxicosis. Clin Nucl Med 2000, 25: 341–7.
Bjøro T, Holmen J, Krüger Ø, et al. Prevalence of thyroid disease, thyroid dysfunction and thyroid peroxidase antibodies in a large, unselected population. The Health Study of Nord-Trondelag (HUNT). Eur J Endocrinol 2000, 143: 639–47.
Canaris GJ, Manowitz NR, Mayor G, Ridgway EC. The Colorado thyroid disease prevalence study. Arch Intern Med 2000, 160: 526–34.
Hollowell JG, Staehling NW, Flanders WD, et al. Serum TSH, T(4), and thyroid antibodies in the United States population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III). J Clin Endocrinol Metab 2002, 87: 489–99.
Laurberg P, Pedersen KM, Hreidarsson A, Sigfusson N, Iversen E, Knudsen PR. Iodine intake and the pattern of thyroid disorders: a comparative epidemiological study of thyroid abnormalities in the elderly in Iceland and in Jutland, Denmark. J Clin Endocrinol Metab 1998, 83: 765–9.
Surks MI, Ocampo E. Subclinical thyroid disease. Am J Med 1996, 100: 217–23.
Canbaz F, Basoglu T, Kececi D, Yapici O, Alkurt M. Scintigraphic patterns in patients with subclinical hyperthyroidism. Hell J Nucl Med 2004, 7: 203–5.
Charkes ND. The many causes of subclinical hyperthyroidism. Thyroid 1996, 6: 391–6.
Kasagi K, Takeuchi R, Misaki T, et al. Subclinical Graves’ disease as a cause of subnormal TSH levels in euthyroid subjects. J Endocrinol Invest 1997, 20: 183–8.
Stott DJ, McLellan AR, Finlayson J, Chu P, Alexander WD. Elderly patients with suppressed serum TSH but normal free thyroid hormone levels usually have mild thyroid overactivity and are at increased risk of developing overt hyperthyroidism. Q J Med 1991, 78: 77–84.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Bjørndal, M.M., Sandmo Wilhelmsen, K., Lu, T. et al. Prevalence and causes of undiagnosed hyperthyroidism in an adult healthy population. The Tromsø study. J Endocrinol Invest 31, 856–860 (2008). https://doi.org/10.1007/BF03346431
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF03346431