Thyroxine withdrawal is accompanied by decreased circulating levels of insulin-like growth factor-binding protein-1 in thyroidectomized patients.

Abstract

We carried out a study on the effect of T4 withdrawal on serum insulin-like growth factor-binding protein-1 (IGFBP-1) levels in 10 thyroidectomized patients with papillary thyroid cancer receiving T4 replacement therapy. As controls we also measured serum sex hormone-binding globulin (SHBG) levels, known to be regulated by T4. Each patient acted as his/her own control, studied both before and 30 days after T4 withdrawal. On the average, the IGFBP-1 level decreased by 36% from 66 +/- 9 to 44 +/- 8 micrograms/L (mean +/- SE; P = 0.0007) during T4 withdrawal. The SHBG level decreased by 47% from 78 +/- 17 to 46 +/- 13 nmol/L (P = 0.0001). The fasting insulin levels were unaffected by T4 withdrawal. There also was an 18% decline in the serum IGF-I concentration after T4 withdrawal (P = 0.011). It is concluded that in athyreotic patients receiving T4, withdrawal of the drug decreases serum IGFBP-1 and SHBG concentrations and IGF-I levels. In view of the possible role of IGFBP-1 in glucose counterregulation, these results indicate a novel mechanism by which T4 may exert its metabolic action on liver carbohydrate metabolism.

Growth hormone/insulin-like growth factor axis in patients with subclinical thyroid dysfunction

“…Main results of these in vivo investigations suggest that there is an increase in serum levels of IGF-I in patients with hyperthyroidism [8,13,15,17,18], and a decrease of these values in patients with hypothyroidism [8][9][10]12]. IGFBP-3 concentrations have been found to be increased in hyperthyroidism [8,12,13,15], and decreased [12] or unmodified [8] in hypothyroidism.…”

“…There have been a number of studies examining the effects of thyroid status on serum concentrations of IGF-I and its binding proteins in patients with thyroid dysfunction [8][9][10][11][12][13][14][15][16]. Main results of these in vivo investigations suggest that there is an increase in serum levels of IGF-I in patients with hyperthyroidism [8,13,15,17,18], and a decrease of these values in patients with hypothyroidism [8][9][10]12].…”

Serum Insulin-Like Growth Factor Type 1, Insulin-Like Growth Factor-Binding Protein-1, and Insulin-Like Growth Factor-Binding Protein-3 Concentrations in Patients with Thyroid Dysfunction

“…I NCREASING EVIDENCE for a relationship between thyroid hormone and growth hormone/insulin-like growth factor (GH/IGF) axis has recently been found (1)(2)(3)(4)(5)(6). GH/IGF axis affects growth and function of the thyroid, as well as thyroid hormone metabolism (7)(8)(9).…”

“…There have been a number of studies examining the effects of thyroid status on serum concentrations of IGF-1 and its binding proteins in patients with thyroid dysfunction (1)(2)(3)(4)6,(19)(20)(21)(22). Main results of these in vivo investigations suggest that there is an increase in serum levels of IGF-1 in patients with hyperthyroidism (1,5,19,21,23), and a decrease of these values in patients with hypothyroidism (1,2,3,6).…”

“…IGFBP-3 concentrations have been found to be increased in hyperthyroidism (1,6,19,21) and decreased (6) or unmodified (1) in hypothyroidism. IGFBP-1 concentration in patients with hypothyroidism has been found to be decreased (2)(3)(4) or unmodified (1), and a few studies have dealt with IGFBP-1 concentrations in hyperthyroid patients (1). Most of the studies reported so far have been performed in a limited number of patients and with no comparison with a control group of euthyroid subjects.…”