Published: 27 July 1973
Growth Hormone Regulation by Melatonin and Serotonin
G. A. SMYTHE & L. LAZARUS
Nature volume 244, pages230–231(1973)Cite this article

Abstract
THERE is evidence to suggest the existence of a pineal gland substance which moderates growth both in man and the rat. In man, non-parenchymal tumours, such as gliomas or teratomas which result in destructive lesions of the pineal gland, are associated with precocious puberty1,2 and it has been hypothesized that such lesions prevent the pineal from secreting gonadal2 and growth3,4 inhibitory factors. It was recently reported5 that the ability of the pineal gland to influence both growth and gonadal development may be due to two distinct physiological mechanisms. Rats which are blinded or kept in constant darkness show reduced body weight4,5, reduced tibeal length4, and reduced accessory organ weights4 as well as retarded puberty2,5,6. Blinded rats were also found4 to have significantly reduced pituitary gland stores of growth hormone. The effects of blinding or constant darkness on growth and growth hormone stores were abolished by pinealectomy4,7—a procedure also found8 to increase the gain of body weight in otherwise normal rats. Pinealectomy has also been reported to result in increased growth of experimental tumours in rats9. The observation10 of a diurnal fluctuation in the secretion of growth hormone in the rat further suggests that the lighting regime can modify this release. When lighting is reduced, concentrations of the pineal hormone melatonin (N-acetyl-o-methylserotonin) are increased because it is synthesized within the pineal gland from serotonin (5-hydroxytryptamine) by the action of the enzymes serotonin-N-acetyltransferase and hydroxyindole-o-methyltransferase, both of which exhibit their highest activities in the absence of light11,12. The fact that the conditions favouring high melatonin production correlate with those which cause reduced growth (and the other way round) suggests that melatonin has an inhibitory role in growth hormone secretory mechanisms. Collu et al.13 demonstrated that intraventricular injections of serotonin stimulate secretion of growth hormone in the rat, and they proposed that in this animal secretion of growth hormone is controlled through serotoninergic pathways. Serotonin has also been implicated as the stimulus for secretion of growth hormone after the onset of slow-wave (non-rapid eye movement, NREM) sleep in normal humans14. It thus seems that serotonin and its pineal derivative, melatonin, may have opposing effects on the secretion of growth hormone. We describe here experiments which support this contention.

Growth Hormone Regulation by Melatonin and Serotonin | Nature
https://www.nature.com/articles/244230a0

　

Br J Sports Med. 2006 Jul; 40(Suppl 1): i35–i39.

Human growth hormone doping in sport
M Saugy, N Robinson, C Saudan, N Baume, L Avois, and P Mangin

Abstract
Background and objectives
Recombinant human growth hormone (rhGH) has been on the list of forbidden substances since availability of its recombinant form improved in the early 1990s. Although its effectiveness in enhancing physical performance is still unproved, the compound is likely used for its potential anabolic effect on the muscle growth, and also in combination with other products (androgens, erythropoietin, etc.). The degree of similarity between the endogenous and the recombinant forms, the pulsatile secretion and marked interindividual variability makes detection of doping difficult. Two approaches proposed to overcome this problem are: the indirect method, which measures a combination of several factors in the biological cascade affected by administration of GH; and the direct method, which measures the difference between the circulating and the recombinant (represented by the unique 22 kD molecule) forms of GH. This article gives an overview of what is presently known about hGH in relation to sport. The available methods of detection are also evaluated.

Growth hormone and exercise
The effect of acute exercise on production of GH in the body has been widely described in the literature.7 The concentration of hGH in blood increases with time for a given work intensity and can increase 10‐fold during prolonged moderate exercise. During more intensive exercise (with accumulation of lactate at 70% Vo2 max for a short term period such as 10–20 minutes) hGH will increase by 5–10‐fold.8 With short exercise durations, levels of GH will generally peak at 15–30 minutes after the exercise. Furthermore, it appears that hGH response is more closely related to the peak intensity of exercise than the total work output.9 Endurance training generally amplifies the pulsatile release of growth hormone, elevating the GH amplitude. This appears evident when the training is very hard and above the aerobic threshold.10

Apart from exercise related increase, hGH secretion can be affected by other factors—for example, GH secretion is increased in hypoglycaemia, increased temperature, and stress, whereas it decreases in obesity, or with a carbohydrate‐rich diet and intake of β2 adrenergic agonists. Thus, it is hard to differentiate between the physiological increase in hGH levels seen in exercise and what can be from external hGH administration (as in doping). This problem makes the purely quantitative approach of measuring directly the total circulating GH not feasible in case of doping, except if the conditions of collection of biological samples are well controlled.

Human growth hormone doping in sport
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2657499/

　

Pituitary gland - the most important factor for height development
https://blog.nubest.com/pituitary-gland-the-most-important-factor-for-height-development-135705/