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GROWTH HORMONE SECRETION AND PLASMA SOMATOMEDIN‐C IN PRIMARY HYPOTHYROIDISM
Author(s) -
CHERNAUSEK S. D.,
UNDERWOOD LOUIS E.,
UTIGER R. D.,
WYK J. J.
Publication year - 1983
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.1983.tb00007.x
Subject(s) - somatomedin , endocrinology , medicine , euthyroid , thyroid , hormone , growth hormone , secretion , chemistry
SUMMARY The effect of thyroid hormone deficiency on plasma immunoreactive somato‐medin‐C concentrations, growth hormone (GH) secretion in response to provocative stimuli, and the plasma somatomedin‐C response to exogenous GH was studied in patients with primary hypothyroidism. Plasma Somatomedin‐C concentrations were below the 95% confidence interval in 11 of 12 hypothyroid patients (mean ± SD=0·27·0±14 U/ml). With thyroid hormone therapy the mean plasma somatomedin‐C level increased four‐fold (1·00·0±43 U/ml). The capacity to secrete GH in response to pharmacological agents was impaired in 3 of the 6 hypothyroid patients tested and normal in the remainder. When the same 6 patients were given a single intramuscular injection of GH (0·1 U/kg) plasma somatomedin‐C concentrations increased four‐fold by 28 h after the injection. The magnitude of the somatomedin‐C response was equal to or greater than that reported for euthyroid GH deficient subjects treated similarly. This study shows that plasma somatomedin‐C concentrations are diminished by hypothyroidism. The decreased somatomedin‐C levels do not appear to result from resistance to the stimulatory effect of GH, but may be either a result of diminished GH secretion or may be due to direct effects of hypothyroidism upon somatomedin production.