Slight Effect of<scp>l</scp>-Tryptophan on Growth Hormone Release in Normal Human Subjects<sup>1</sup>

Müller, E. E.; Brambilla, F; Cavagnini, Francesco; Peracchi, M.; Panerai, A

doi:10.1210/jcem-39-1-1

Cited by 65 publications

(22 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…111 In turn, aminoacids participate in the regulation of GH release. Indeed, high protein meals and administration of basic (arginine and ornithine) and aromatic (tryptophan) aminoacids, stimulate GH secretion in normal subjects, 112,113 probably because of a decrease in hypothalamic SRIH. 114 As mentioned above, an impairment of the GH response to arginine, alone or combined with GHRH, is well documented in obesity.…”

Section: Nefamentioning

confidence: 99%

Growth hormone in obesity

1999

View full text Add to dashboard Cite

Growth hormone (GH) secretion, either spontaneous or evoked by provocative stimuli, is markedly blunted in obesity. In fact obese patients display, compared to normal weight subjects, a reduced half-life, frequency of secretory episodes and daily production rate of the hormone. Furthermore, in these patients GH secretion is impaired in response to all traditional pharmacological stimuli acting at the hypothalamus (insulin-induced hypoglycaemia, arginine, galanin, L-dopa, clonidine, acute glucocorticoid administration) and to direct somatotrope stimulation by exogenous growth hormone releasing hormone (GHRH). Compounds thought to inhibit hypothalamic somatostatin (SRIH) release (pyridostigmine, arginine, galanin, atenolol) consistently improve, though do not normalize, the somatotropin response to GHRH in obesity. The synthetic growth hormone releasing peptides (GHRPs) GHRP-6 and hexarelin elicit in obese patients GH responses greater than those evoked by GHRH, but still lower than those observed in lean subjects. The combined administration of GHRH and GHRP-6 represents the most powerful GH releasing stimulus known in obesity, but once again it is less effective in these patients than in lean subjects. As for the peripheral limb of the GH ± insulin-like growth factor I (IGF-I) axis, high free IGF-I, low IGF-binding proteins 1 (IGFBP-1) and 2 (IGFBP-2), normal or high IGFBP-3 and increased GH binding protein (GHBP) circulating levels have been described in obesity. Recent evidence suggests that leptin, the product of adipocyte speci®c ob gene, exerts a stimulating effect on GH release in rodents; should the same hold true in man, the coexistence of high leptin and low GH serum levels in human obesity would ®t in well with the concept of a leptin resistance in this condition. Concerning the in¯uence of metabolic and nutritional factors, an impaired somatotropin response to hypoglycaemia and a failure of glucose load to inhibit spontaneous and stimulated GH release are well documented in obese patients; furthermore, drugs able to block lipolysis and thus to lower serum free fatty acids (NEFA) signi®cantly improve somatotropin secretion in obesity. Caloric restriction and weight loss are followed by the restoration of a normal spontaneous and stimulated GH release. On the whole, hypothalamic, pituitary and peripheral factors appear to be involved in the GH hyposecretion of obesity. A SRIH hypertone, a GHRH de®ciency or a functional failure of the somatotrope have been proposed as contributing factors. A lack of the putative endogenous ligand for GHRP receptors is another challenging hypothesis. On the peripheral side, the elevated plasma levels of NEFA and free IGF-I may play a major role. Whatever the cause, the defect of GH secretion in obesity appears to be of secondary, probably adaptive, nature since it is completely reversed by the normalization of body weight. In spite of this, treatment with biosynthetic GH has been shown to improve the body composition and the metabolic ef®cacy of lean body mass in obese pa...

show abstract

Section: Nefamentioning

confidence: 99%

Growth hormone in obesity

1999

View full text Add to dashboard Cite

show abstract

“…In fact, other studies have yielded variable re sponses of growth hormone to 5-HTP. An increase [17] or no change [18] in growth hormone concentrations have been observed by oral administration of 5-HTP in small dose (150 mg in adults) or in large dose (150 mg/kg in adults), respectively.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of 5-Hydroxytryptophan Administration as a Test of Pineal Function in Humans

Cavallo¹,

Richards²,

Meyer³

et al. 1987

Horm Res

View full text Add to dashboard Cite

We tested the hypothesis that acute 5-hydroxytryptophan (5-HTP) administration would cause an increase in concentrations of plasma melatonin to levels observed during the spontaneous nocturnal melatonin surge. We administered 5-HTP orally (5-12 mg/kg) to 10 healthy children and 5 healthy adults, and measured melatonin concentrations in plasma samples obtained every 30 min for 3-6 h. There was no appreciable increase in melatonin after 5-HTP stimulation, even though a melatonin increase has been reported in sheep treated with 5-HTP.

show abstract

“…Muller et al, 1974) have appeared on the effect of 5-HTP on plasma hGH levels. In contrast to our findings, they found no stimulatory effect of 5-HTP on plasma hGH.…”

Section: Discussionmentioning

confidence: 99%

Effect of Adrenergic-blocking Agents on Plasma Growth Hormone Response to L-5-Hydroxytryptophan (5-HTP) in Man

Nakai

Imura

1974

Endocrinol Japon

View full text Add to dashboard Cite

Slight Effect ofl-Tryptophan on Growth Hormone Release in Normal Human Subjects¹

Cited by 65 publications

References 0 publications

Growth hormone in obesity

Growth hormone in obesity

Evaluation of 5-Hydroxytryptophan Administration as a Test of Pineal Function in Humans

Effect of Adrenergic-blocking Agents on Plasma Growth Hormone Response to L-5-Hydroxytryptophan (5-HTP) in Man

Contact Info

Product

Resources

About

Slight Effect ofl-Tryptophan on Growth Hormone Release in Normal Human Subjects1

Cited by 65 publications

References 0 publications

Growth hormone in obesity

Growth hormone in obesity

Evaluation of 5-Hydroxytryptophan Administration as a Test of Pineal Function in Humans

Effect of Adrenergic-blocking Agents on Plasma Growth Hormone Response to L-5-Hydroxytryptophan (5-HTP) in Man

Contact Info

Product

Resources

About

Slight Effect ofl-Tryptophan on Growth Hormone Release in Normal Human Subjects¹