Trends of serum thyrotropin concentration and associated factors in urban Pakistan [Karachi]

ABSTRACT

This investigation aimed at assessing trends of TSH levels and associated factors in apparently normal subjects of urban Pakistan [Karachi]. The survey was conducted in 2004 in Lyari, Karachi. Using a geographical imaging system, 85, 520 households were identified, of which 532 were randomly selected; 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. 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 87.8 +/- 15.7 cm repectively. Fifty-nine [18.2%] subjects had TSH>6.0 cm [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. 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