Thyroid-stimulating hormone in hypothyroidism – How high is too high?

Abstract

Background: The prevalence of hypothyroidism in the developed world is about 4-5% and in India is 10.9%. The goal of treating hypothyroidism is to maintain thyrotropin (TSH) levels within the normal reference range. Studies have shown that even within the normal range of TSH, patients with low normal TSH (LNT) have better outcomes when compared to patients with high normal TSH (HNT). Aims and Objectives: Our study aimed to find whether patients treated at a dose of levothyroxine resulting in an LNT had improved clinical outcomes and biochemical parameters, when compared to those on a levothyroxine dose resulting in an HNT. Materials and Methods: 180 patients with hypothyroidism on treatment, who had a TSH of 0.27-4.2mIU/L and had been on treatment with a stable dose of at least 50 micrograms of levothyroxine for at least 6 months were administered the Thyroid Symptom Questionnaire. TSH was assayed. Blood pressure and BMI were measured. Serum lipids were measured by spectrophotometry. Results: We found that patients with LNT and HNT did not differ with respect to cognitive symptoms , feelings of coldness, lethargy and fatigue. However, patients with LNT had a better lipid profile (mean LDL 132.24 in HNT and 115.39 in LNT p= 0.08) and lower BMI (1.045kg/m 2 lower in LNT compared to HNT) compared to HNT. Conclusion: Treating patients with a dose of thyroxine titrated to achieve LNT might decrease the cardiovascular risk by improving the lipid profile and BMI.