Changes in GH-secreting pituitary function following short-term caloric restriction
Butturini, L.; Baroni, M.C.; Mineo, F.; Delsignore, R.
Giornale di Clinica Medica 67(1): 35-38
1986
ISSN/ISBN: 0017-0275 PMID: 3792711 Document Number: 285535
It is known that human Growth Hormone (hGH), among other metabolic effects, has an evident lypolitic action both in vivo and in vitro: it tends to decrease the respiratory Quotient, indicating that fat is utilized as primary fuel. In order to further investigate in this field, we made a study on 6 healthy males, volunteers, aged between 22 and 32 yrs. At first they have been given 0.15 mg clonidine e.v. to the test hGH secretion: this was made under normal dietary condition. After 2 months the test was repeated, following 2 days under a mild hypocaloric (55-60% of the avg. normal food intake) and hypoglucidic (150 gm/day) diet. Blood samples were taken at times .sbd. 15', 0', 15', 30', 45', 60', 90', and 120' and immediately centrifuged and frozen until R.I.A. assay of hGH and PRL. As a result, hGH baseline values were significantly (p < 0.05) higher in group 2; both groups stayed well within normal range. The 2nd group showed a very significant increase in the stimulated values, with a striking difference from the 1st group, in which no response was observed. PRL levels decreased significantly (p < 0.01), both groups sharing the same pattern of changes. Our study confirms the relationships between hGH status and dietary conditions. The increase in hGH integrated areas after stimulation is probably due to the lack of the inhibitory feed-back control brought about by Somatomedin-C, whose levels are known to decrease after reduction of food intake. Receptors for somatomedin have in fact been shown in pituitary gland. Our findings could also explain the lack of hGH response after many provocative tests that is commonly seen even in healthy men.