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.
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