Effect of Oral Administration of Melatonin on Gh Responses to GRF 1–44 in Normal Subjects

Valcavi, Roberto; Diéguez, Carlos; Azzarito, Clorinda; Edwards, C.; Dotti, C; Page, M. D.; Portioli, I; Scanlon, M. F.

doi:10.1111/j.1365-2265.1987.tb00802.x

Cited by 36 publications

(19 citation statements)

References 15 publications

(17 reference statements)

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“…The effect of melatonin to increase exerciseinduced GH secretion in our subjects would therefore suggest that it has an effect on central hypothalamic regulation through either GHRH or somatostatin release. Enhanced GH secretion following melatonin administration has been previously shown by Valcavi et al (5) who studied the GH response to GHRH. It was postulated then that the increased GH response was facilitated through an inhibition of endogenous somatostatin release since the melatonin effect was abolished following the administration of pyridostigmine.…”

Section: Discussionmentioning

confidence: 85%

“…Results from studies which have investigated the effect of melatonin on stimulated GH secretion have been contradictory. Melatonin has been shown to enhance the GH response to GHreleasing hormone (GHRH) (2,5) but not to stimulation with L-dopa (6). A reduction in GH response has been observed following insulin-induced hypoglycaemia (3) and L-tryptophan administration (7).…”

Section: Introductionmentioning

confidence: 99%

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Exercise-induced GH secretion is enhanced by the oral ingestion of melatonin in healthy adult male subjects

et al. 1999

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There is evidence that melatonin may play a role in modulating pituitary secretion, although the mechanisms are unclear. We examined the effects of a single dose of oral melatonin (5 mg) on exerciseinduced GH secretion. In a randomised, double-blind, placebo-controlled study, seven healthy male subjects undertook an initial period of graded bicycle ergometric exercise to determine maximum workload and oxygen uptake (VO 2 max ). Subjects were subsequently studied on two further occasions, receiving either melatonin or placebo in random order at the onset of each study (¹60 min). At 0 min a period of bicycle exercise was performed for 8 min at a workload corresponding to 70 % of that achieved at VO 2 max . Serum GH and IGF-binding protein-1 (IGFBP-1) concentration was measured at 15-min intervals from the onset of the study until 120 min post-exercise. Blood was also sampled for the measurement of plasma glucose, insulin, non-esterified fatty acids, IGFBP-3, melatonin and vasopressin concentration. There was an exercise-induced increase in GH concentration following melatonin which was greater compared with placebo as assessed by both area under the curve (P < 0.01) and peak increase in GH levels (P < 0.01). The peak increase in IGFBP-1 levels post-exercise was also significantly greater following melatonin compared with placebo (P < 0.01) but did not quite reach levels of significance as measured by area under the curve (P = 0.07). Since exercise-induced GH secretion is thought to be mediated predominantly through a hypothalamic pathway, it seems likely that melatonin facilitates GH secretion at a hypothalamic level.

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Section: Discussionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Exercise-induced GH secretion is enhanced by the oral ingestion of melatonin in healthy adult male subjects

et al. 1999

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“…The effects of MEL on GH secretion are not consistent and are still controversial at present. For example, the stimulatory effect of MEL on GH secretion was observed when MEL was administered in the morning [27,29,30] when endogenous MEL levels are low [13]. The administration of MEL had no effect on GH secretion when it was given at 1700 [13].…”

Section: Discussionmentioning

confidence: 99%

Effect of Melatonin Injected into the Third Ventricle on Growth Hormone Secretion in Holstein Steers

Kasuya

Kushibiki

Sutoh

et al. 2006

The Journal of Veterinary Medical Science

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ABSTRACT. The effects of melatonin (MEL) injection into the third ventricle (3V) on growth hormone (GH) secretion were investigated in conscious Holstein steers. A stainless steel cannula was stereotaxically implanted in the 3V based on the ventriculogram. In Exp. 1, three doses of MEL (100, 300 or 600 µg) were injected into the 3V through the cannula and the GH concentration after the injection was determined. In Exp. 2, intracerebroventricular (icv) and intravenous (iv) injections of MEL (100 µg) and GH-releasing hormone (GHRH; 0.25 µg/kg body weight), respectively, were performed simultaneously to examine the effect of MEL on GHRH-induced GH release. The icv injection of MEL significantly stimulated GH release at 100 µg. The increase in GH concentrations by 100 µg of MEL was persistent. Intravenous injection of GHRH dramatically increased GH release. The injection of MEL did not alter GHRH-induced GH release. These results suggest that MEL stimulates GH secretion possibly through the hypothalamus in cattle. KEY WORDS: cattle, melatonin, somatotropic axis, stereotaxic, third ventricle.J. Vet. Med. Sci. 68(10): 1075-1080, 2006 Growth hormone (GH) is a very important factor for livestock production [6]. GH-releasing hormone (GHRH) and somatostatin (SS) from the hypothalamus are primary factors controlling GH secretion in mammals. In addition to GHRH and SS, many neuromodulators have been considered to be involved in GH release regulation in many species. Although the central regulatory mechanism of GH secretion has been studied in sheep using hypophyseal portal blood sampling technique [4], such information is not well obtained in cattle.The evidences have shown the possibility that melatonin (MEL) from the pineal gland is one of those factors controlling GH secretion; however, the exact effect of MEL on GH secretion is controversial. For example, in humans it was reported that MEL induced an increase in GH levels [27,29]; however, other groups obtained no effects of MEL on GH secretion [13,31]. The intramuscular injection of MEL decreased GH secretion in prepubertal boys and the same dose of MEL increased GH level in some pubertal subjects [17]. In vitro experiments showed that MEL reduced GH secretion from rat pituitary cells [8]. These variations of the effects of MEL on GH secretion could be caused by the differences in the experimental and physiological conditions, and there might be inter-species differences regarding the role of MEL in the regulation of GH secretion.The purpose of the present study was to determine the role of MEL in the regulatory system of GH secretion in cattle. Since MEL has been reported to stimulate GH release via the hypothalamus [23,29], the technique for the direct injection of MEL into the third ventricle (3V) at three doses (100, 300 and 600 µg) was used. We also assessed whether MEL affects GHRH-induced GH release to reveal the involvement of the hypothalamus in GH secretion modulated by MEL. MATERIALS AND METHODS Animals:Eleven Holstein steers (7 to 8 mo old at the time of su...

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“…Melatonin administration releases GH both in rats [61] and man [62, 63]. The administration of a 3‐mg dose of melatonin during 14 nights to elderly patients with chronic primary insomnia brought about a significant reduction in wake time after sleep onset, and an increase in sleep efficiency and stage 2 sleep [64].…”

Section: Melatonin and Growth Hormone Releasementioning

confidence: 99%

Melatonin effects on bone: experimental facts and clinical perspectives

Cardinali

Ladizesky

Boggio

et al. 2003

Journal of Pineal Research

204

195

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Bone formation proceeds through a remodeling process that runs continuously, involving the resorption of old bone by osteoclasts, and the subsequent formation of new bone by osteoblasts. This is controlled by growth factors and cytokines produced in bone marrow microenvironment and by the action of systemic hormones, like parathyroid hormone, estradiol or growth hormone (GH). One candidate for hormonal modulation of osteoblast and osteoclast formation is melatonin. Because circulating melatonin declines with age, its possible involvement in post-menopausal and senescence osteoporosis is considered. This review article discusses early studies on melatonin-bone relationships and recent data that suggest a direct effect of melatonin on bone. Melatonin could act as an autacoid in bone cells as it is present in high quantities in bone marrow, where precursors of bone cells are located. Melatonin dose-dependently augmented proteins that are incorporated into the bone matrix, like procollagen type I c-peptide. Osteoprotegerin, an osteoblastic protein that inhibits the differentiation of osteoclasts is also augmented by melatonin in vitro. Another possible target cell for melatonin is the osteoclast, which degrades bone partly by generating free radicals. Melatonin through its free radical scavenger and antioxidant properties may impair osteoclast activity and bone resorption. At least in one study melatonin was both inhibitory to osteoclastic and osteoblastic cells. Therefore, the documented bone-protecting effect of melatonin in ovariectomized rats can depend in part on the free radical scavenging properties of melatonin. Additionally, melatonin may impair development of osteopenia associated with senescence by improving non-rapid eye movement sleep and restoring GH secretion. Whether melatonin can be used as a novel mode of therapy for augmenting bone mass in diseases deserves to be studied.

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Effect of Oral Administration of Melatonin on Gh Responses to GRF 1–44 in Normal Subjects

Cited by 36 publications

References 15 publications

Exercise-induced GH secretion is enhanced by the oral ingestion of melatonin in healthy adult male subjects

Exercise-induced GH secretion is enhanced by the oral ingestion of melatonin in healthy adult male subjects

Effect of Melatonin Injected into the Third Ventricle on Growth Hormone Secretion in Holstein Steers

Melatonin effects on bone: experimental facts and clinical perspectives

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