Association of TSH Levels in the Therapeutically Neglected Range of 6.5–8 mIU/L with Significant Changes in Liver and Kidney Function: A Retrospective Study of the Kashmiri Population

Abstract

Background: The thyroid gland secretes hormones crucial for growth, differentiation, regulation of metabolic processes, and homeostasis. In response to underactivity of this gland, the pituitary secretes thyrotropin, also known as the thyroid-stimulating hormone (TSH). Medication for thyroid hypofunction is usually started when TSH levels exceed 10 mIU/L. However, we hypothesize that TSH levels much below this therapeutic threshold level may herald significant renal and hepatic dysfunction. The present study was thus conducted to assess liver and kidney function parameters in cases having TSH in the subclinical range with particular focus on the therapeutically neglected (6.5–8 mIU/L) range. Methods: Hospital laboratory archives of 297 adults with laboratory evidence of hypothyroidism, that is, TSH > 6.5 mIU/L, were retrieved and compared with data obtained from 430 euthyroid hospital controls, that is, TSH < 2.5 mIU/L, also from the same period. The thyroid profile and clinical chemistry analyses were performed on Beckman Coulter’s UniCel DxI 800 and AU 5800, respectively. SPSS version 20 was used to analyze the results. Results: Significant differences in triiodothyronine (T3), thyroxine (T4), TSH, urea, creatinine, total bilirubin, total protein (TP), and liver enzymes were observed between cases with TSH > 6.5 mIU/L and controls (P < 0.05). There was also a significant difference in T4, TSH, urea, creatinine, total bilirubin, albumin and aspartate aminotransferase (AST) among cases with TSH in the range of 6.5–8 mIU/L when compared with controls (P < 0.05). A correlation of T3 with TSH, urea, and creatinine was seen (P < 0.05). No correlations between TSH and other clinical chemistry parameters could be observed. However, in the 6.5–8 mIU/L subgroup, correlation of TSH was seen with TP and albumin only. Conclusion: Authors found that, as a rule, subtle renal and hepatic dysfunction were established in cases with TSH levels <8 mIU/L, which was below the typical “therapeutic cut-off” of 10 mIU/L. Accordingly, we advocate against incautiousness and suggest regular monitoring, especially in the 6.5–8 mIU/L range.