Complex Rhythmicity of Growth Hormone Secretion in Humans

Abstract

To better characterize the 24 hr GH secretion pattern in humans, we studied frequently sampled 24 hr GH profiles in 93 young (18-45 years of age) healthy, fed volunteers: men (n=67) and women (n=26) with BMI<26 kg/m(2). Analysis of the composite GH series in men revealed 3 significant GH "waves" with peaks occurring at midnight (p<0.0001), at noon (p<0.02) and at 1800 h (p<0.0001). In women, similar pattern was seen, with three GH "waves" peaking at midnight (p<0.0001), 1100 h (p<0.02) and at 1600 h (p<0.002). We conclude that the 24 hr rhythmicity of GH secretion is far more complex than currently appreciated. The attribution of the two daytime GH "waves" to food consumption is unlikely but cannot be excluded at the present time. The complex temporal pattern of pulsatile GH secretion may have important effects on regulation of target cell function.

Complex Rhythmicity and Age Dependence of Growth Hormone Secretion Are Preserved in Patients With Acromegaly: Further Evidence for a Present Hypothalamic Control of Pituitary Somatotropinomas

“…Figure 1A shows the mean composite profile of lntransformed ratios of the hourly mean over daily median for the control group. The analysis of the daytime GH secretion in this group shows the presence of a statistically significant (P Ͻ .001) 3-wave GH secretion pattern, as previously demonstrated elsewhere (13). The maximal ratios occurred at 1200 PM, at 5:00 PM, and, most prominently, at 1:00 AM.…”

“…In a small sample of treated and untreated acromegalic patients with relatively homogeneous GH outputs, we have previously suggested the persistence of the nocturnal GH augmentation (12). Subsequently we have shown that the rhythmicity of GH secretion in humans is much more complex than a simple presence of the so-called nocturnal augmentation and consists of 3 distinct major waves of GH output, at 11:00 AM/12:00 PM, at 4:00 PM/5:00 PM, and 12:00/2:00 AM, with a sexually dimorphic pattern (13).…”

Male-female differences in 6-sulfatoxymelatonin excretion in hypopituitary patients

“…This phenomenon could be possibly explained by the role of estrogens. It could also be related to a well-known physiological pattern of GH, which is released largely at night in complex ultradian pulses that do not readily follow a classic circadian pattern (10). Indirectly, the clock system directs secretion through slow-wave sleep which is strongly associated with GH release, although the precise mechanism of circadian influence is not understood.…”

“…GH is released largely at night in complex ultradian pulses that do not readily fit a classic circadian pattern. Indirectly, the clock system directs secretion through slow-wave sleep, which is strongly associated with GH release, although the precise mechanism of circadian influence is not understood (10). We have demonstrated in a recent paper decreased 6-sulphatoxymelatonin (6-SM) excretion in male GH-deficient children and adolescents (11).…”

Circadian Proteomics and Its Unique Advantage for Discovery of Biomarkers of Heart Disease

“…Patients with hypertensive heart disease exhibited a greater increase in PRA during sleep-time as compared to normotensive patients (Tuck et al, 1985). Finally, growth hormone secretion by the anterior pituitary gland is pulsatile and has a circadian rhythm with the highest peak occurring at midnight (Surya et al, 2006). Growth hormone is involved in regulation of cardiac metabolism and contractility, reviewed by (Volterrani et al, 2000).…”