Trends of Serum Thyrotropin Concentration and Associated Factors in Urban Pakistan (Karachi)

Background:This investigation aimed at assessing trends of TSH levels and associated factors in apparently normal subjects of urban Pakistan (Karachi).
Materials and Methods: The survey was conducted in 2004 in Lyari, Karachi. Using a geographical imaging system, 85, 520 households were identified, of which 532 were randomly se-lected; 867 adults aged ≥25 years consented to take part in the study. Blood samples from 324 subjects were available for analyses. Subjects with previous history of thyroid disorders were excluded.
Results: Mean age of subjects was 40.8±14.13 years; 68.2% were females; mean values of waist circumference of males and females were 89.5±16 cm and 87.8±15.7 cm respectively. Fifty-nine (18.2%) subjects had TSH>6.0 (mU/L) based on the ELISA laboratory reference range, used for the estimation of TSH. Based on the American Thyroid Association (ATA) guidelines, 159 (49.07%) subjects had TSH<2.5, while 76 (23.45%) subjects with TSH between 2.5–4.0 mU/L as per ATA definition were in the “at risk” category. Thirty subjects (9.26%) had TSH levels between 4.1–6.0 mU/L. A significant correlation was found between TSH and BMI and waist circumference, whereas a weak, non significant one was observed between TSH and waist hip ratio. A strong association between overweight (BMI>23) and elevated serum TSH concentration (TSH>4.1 mU/L) was also observed.
Conclusion: This spectrum of TSH levels highlighted a high prevalence of increased serum TSH levels in the population studied, a trend that was associated with obesity and various lipid abnormalities. Further population based studies are needed to correlate these findings with clinical parameters of hypothyroidism.