The TSH levels and risk of hypothyroidism: Results from a population based prospective cohort study in an Iranian adult’s population
Authors
Affiliations
- 1Isfahan Endocrine and Metabolism Research Center, Isfahan University of Medical Sciences, Isfahan, Iran. Electronic address: aminorroaya@med.mui.ac.ir.
- 2Isfahan Endocrine and Metabolism Research Center, Isfahan University of Medical Sciences, Isfahan, Iran. Electronic address: meamar@pharm.mui.ac.ir.
- 3Isfahan Endocrine and Metabolism Research Center, Isfahan University of Medical Sciences, Isfahan, Iran. Electronic address: m_amini@med.mui.ac.ir.
- 4Isfahan Endocrine and Metabolism Research Center, Isfahan University of Medical Sciences, Isfahan, Iran; Department of Biostatistics and Epidemiology, School of Public Health, Isfahan University of Medical Sciences, Isfahan, Iran.
- 5Central London Community Health Trust, UK.
- 6Isfahan Endocrine and Metabolism Research Center, Isfahan University of Medical Sciences, Isfahan, Iran.
Abstract
Objective: The aim of current study was to assess the relationship between serum TSH levels and hypothyroidism risk in the euthyroid population.
Methods: In a population-based cohort study, a total of 615 individuals with a normal baseline TSH, from of total population (n=2254) in 2006, were followed up for 6years. TSH, total T4, thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb) were measured. The relative risk (RR) and 95% confidence interval (95%CI) were calculated based on logistic regression. The Receiver Operating Characteristic (ROC) analysis along with area under the curve (AUC) was used to prediction of future hypothyroidism.
Results: TSH level in 2006 was a significant predictor for overt hypothyroidism, in the total population (RR=3.5) and female (RR=1.37) (all, P value<0.05). A cutoff value of TSH at 2.05mIU/L [AUC: (CI95 %), 0.68 (0.44-0.92; P=0.05)] was obtained for differentiating the patients with overt hypothyroidism from euthyroid. However, this cut off was not observed when we included only negative TPO and TgAbs people in 2006. The RR of hypothyroidism increased gradually when TSH level increased from 2.06-3.6mIU/L to >3.6mIU/L in the total population and both sexes. In women, the risk of overt hypothyroidism was significantly higher in subjects with TSH above 3.6 than those subject with THS levels≤2.05 [RR: (CI95 %), 20.57(2.-207.04), P value<0.05]. Conclusion: A cutoff value of TSH at 2.05mIU/L could predict the development of overt hypothyroidism in future. However, it was not applicable for people with negative TPOAb and negative TgAb.
Keywords: Euthyroidism; Hypothyroidism; Risk; TSH.