Insulin-like growth factor I alters peripheral thyroid hormone metabolism in humans: Comparison with growth hormone

Mehboob A. Hussain, Ole Schmitz, Jens O.L. Jorgensen, Jens S. Christiansen, Jorgen Weeke, Christoph Schmid, E. Rudolf Froesch

Research output: Contribution to journalArticle

Abstract

Insulin-like growth factor I (IGF-I) is considered to mediate some of the growth-promoting and metabolic effects of growth hormone (GH). Growth hormone treatment of healthy and GH-deficient subjects is accompanied by increased conversion of thyroxine (T4) to triiodothyronine (T3) in peripheral tissues. Whether these effects are mediated by IGF-I is unknown. To assess the respective roles of these hormones on thyroid hormone metabolism we have treated two groups of subjects. The first group consisted of eight healthy subjects who were treated with IGP-I (10 μg·kg-1· h-1 sc for 5 days). The second group consisted of eight subjects with combined GH and thyrotropin (TSH) deficiency due to acquired pituitary disease. They were treated with IGP-I (10 μg·kg-1·h-1 sc for 7 days), GH (2 IU m-2 sc q.i.d.) or both hormones together. The IGF-I treatment in healthy subjects led to an increase in free T3 (FT3) and a reduction in TSH levels, whereas FT4 and total T4 (TT4) levels remained unchanged. In the second group - in which ail subjects were substituted with oral L-thyroxine - treatment with IGF-I led to an elevation of FT3 in the face of unchanged T4 levels. Growth hormone alone and GH plus IGF-I resulted in a more pronounced elevation in T4 level. The results suggest that IGF-I partially mediates the well-known effects of GH on peripheral conversion of T4 to T3 However, GH has more pronounced effects on thyroid hormones that apparently are not mediated by IGF-I.

Original languageEnglish (US)
Pages (from-to)563-567
Number of pages5
JournalEuropean Journal of Endocrinology
Volume134
Issue number5
DOIs
StatePublished - May 1996
Externally publishedYes

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Endocrinology

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