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lntra‐ and Inter‐Individual Variability in Growth Hormone Responses to Growth Hormone‐Releasing Hormone *
Author(s) -
Fornito Maria C.,
Calogero Aldo E.,
Mongioi Alessandro,
Coniglione Francesca,
Vicari Enzo,
Moncada Maria Luisa,
D'Agata Rosario,
Merriam George R.
Publication year - 1990
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1990.tb00397.x
Subject(s) - endocrinology , medicine , ultradian rhythm , somatostatin , hormone , growth hormone–releasing hormone , growth hormone , stimulation , bolus (digestion) , biology , circadian rhythm
Normal subjects show a wide range of growth hormone (GH) responses to growth hormone‐releasing hormone (GHRH) stimulation, but it is uncertain whether this variability reflects differences among individuals or whether it would also be observed on repeated tests of the same subject. To clarify this, we tested nine normal men repeatedly with iv bolus doses of 1 μg/kg GHRH(1–44)NH 2 . Most subjects showed wide variations in their GH responses on repeated testing, and the intra‐individual variability was nearly as great as the inter‐individual variability in responses, accounting for about two‐thirds of the overall variance. A minority of subjects had lower and less variable responses. Ultradian fluctuations in hypothalamic somatostatin secretion may account for this marked intra‐individual variability.