Serum insulin levels and the degree of thyroid dysfunction in hypothyroid women

Among the peripheral effects of thyroid hormone action, their influence on insulin is of great interest and conflicting data on this subject are available. Despite various studies already performed, of concern is whether insulin levels change in line with a deterioration of thyroid function. In this study, we investigated serum serum insulin levels and their correlations with thyroid-stimulating hormone (TSH), free thyroxine (FT4) and free triiodothyronine (FT3) in hypothyroid women.

Study group consisted of 22 women with a history of total thyroidectomy and radioiodine ablation performed for thyroid cancer, without diabetes or glucose intolerance. After six-weeks of thyroxine withdrawal, subjects were admitted to the Department of Endocrinology of the Poznan University of Medical Sciences to perform this study.

Plasma glucose and insulin were respectively: 4.76+/-0.47 mmol/L and 7.19+/-4.22 microU/mL. Serum TSH, FT4 and FT3 were respectively: 91.66+/-58.59 microU/mL, 2.65+/-2.19 pmol/L, and 1.53+/-1.00 pmol/L. Correlations were: r of -0. 4381 and P of 0.0414, r of -0.2368 and P of 0.2887, and r of 0.3954 and P of 0.0686 for insulin and FT4, insulin and FT3, and insulin and TSH, respectively. The only significant correlation was an inverse correlation between insulin and FT4.

In profound hypothyroidism insulin concentrations correlate with FT4 only, but not with FT3 or TSH.