SUBCLINICAL HYPERTHYROIDISM-A COHORT STUDY
Objective: To compare the development of overt hyperthyroidism in a cohort of patients of subclinical hyperthyroidism (SCR) and in subjects with normal thyroid function tests
Study Design: A cohort study.
Place and Duration of study: The study was conducted in the department of Chemical Pathology and Endocrinology, Armed Forces Institute of Pathology, Rawalpindi from Sept 2006 to Sept 2007.
Patients and Methods: Fifty patients of SCR and almost equal number of age and sex-matched subjects with normal Thyroid function test (TFT) were included in the study as controls. Subclinical hyperthyroid patients and controls were followed for a period of one year on a six monthly basis. The patients were examined for signs and symptoms of hyperthyroidism and serum TSH, total T3 and free T4 were estimated. The clinical history, physical examination and TFT results were recorded. Five ml of blood was collected for serum thyroid profile in plain tube. Hormonal analysis (TSH, T4 and T3) was done for the patients and the controls enrolled in the study. The TFTs was analyzed using Chemiluminescence Immunoassay technique on Immulite 2000 an automated, random access, immunoassay analyzer.
Results: Six (12%) out of 50 cases of the SCR patients and 2 (4%) out of 50 controls developed overt hyperthyroidism. SCR had no significant risk for conversion to overt hyperthyroidism as compared to healthy controls in this study. In addition to initial levels of serum TSH were one of important predictor for conversion of SCR to overt hyperthyroidism.
Conclusion: Patients with SCR have no significant risk but showed an increase in frequency of conversion to overt hyperthyroidism (12% in this study) as compared to controls.