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Abstract

Background: Sub-clinical hypothyroidism (SCO) poses diagnostic and management difficulties forpathologists and clinicians. Cases of SCO are now diagnosed with increasing frequencies worldwidemainly because of availability of more sensitive methods for serum TSH, total T3 and free T4 assays.The rate of progression of SCO to overt hypothyroidism varies in different populations. Sub-clinicalhypothyroidism has been suggested as a risk factor for hypothyroid complications. There is a need toidentify and treat patients with SCO before they convert to overt hypothyroidism and developcomplications. Objective was to compare the development of overt hypothyroidism in a cohort ofpatients of sub-clinical hypothyroidism and in subjects with normal thyroid function tests. Methods: Itwas Cohort study conducted at Department of Chemical Pathology and Endocrinology, Armed ForcesInstitute of Pathology, Rawalpindi. Hundred patients of SCO and almost equal number of age and sexmatched subjects with normal Thyroid function test (TFT) were enrolled as healthy controls. Subclinical hypothyroid patients and controls were followed for a period of one year on six monthly bases.The patients were examined for signs and symptoms of hypothyroidism and serum TSH, total T3 andfree T4 were estimated. The clinical history, physical examination and thyroid function tests wererecorded on the pre-designed Performa. Results: Fourteen (14%) out of 100 cases of the SCO patientsdeveloped overt hypothyroidism, SCO had 2.8 times more risk for conversion to overt hypothyroidismas compared to healthy controls. Moreover female gender and initial levels of serum TSH were themost important predictors for conversion of SCO to overt hypothyroidism. Conclusion: The frequencyof conversion to overt hypothyroidism in SCO patients approaches 14% and was more commonlyobserved in female patients.Keywords: Subclinical hypothyroidism, thyroid stimulating hormone, thyroid function tests, overthypothyroidism