Quantitative Assessment Of The Variations In Thyroid Dimensions In Relation To Increase In Serum TSH In Euthyroids

Abstract

Background: Volumetric evaluation of thyroid gland volume (TGV) is one of the criteria determining the iodine status of a population. TGV is the product of 3 dimension of each lobe: Anterio-posterior (AP) x medio-lateral (ML) x and craniocaudal (CC) x correction factor. Objectives: To determine the effect of serum TSH on thyroid dimensions of each lobe and to measure the amount of effect of per unit increase in serum TSH on thyroid dimensions of each lobe in euthyroids. Study Design: It was a cross-sectional study. Setting: The study was conducted at Ziauddin University Hospital, Clifton, Karachi. Methodology: Healthy participants aged 21 years and above were included through convenient sampling. Serum Thyroid stimulating hormone was evaluated and ultrasound of thyroid gland TG of 192 euthyroid participants was performed. Spearman correlation and regression analysis was applied to evaluate the relationship between TSH and TG dimensions Results: Relationship of increase in serum TSH with decrease in light lobe AP dimension was most significant. (r= -0.142 P-Value=0.001) and CC dimension least significant (r= -0.0098 P-Value=0.001). Where as in the left lobe AP dimension decreases significantly with increase serum TSH (r= -0.147 P-value=0.001). 11.7% of total variation in AP dimension, 3.5% of total variation in ML dimension and 6.5% of total variation in CC dimension in right lobe thyroid are because of serum TSH. While 9.5% of the total variation in AP dimension in left lobe is also due to serum TSH. Conclusion: Negative and significant correlation between serum TSH and thyroid dimensions was observed. Serum TSH inversely and significantly affects all the dimensions of the right lobe and only one dimension in the left lobe