Relation between growth hormone and cortisol spontaneous secretion in children

Dual effects of corticoids upon GH release in man have been described: a rapid, potentiating effect and a delayed suppressive one. Many investigators have used pharmacological doses of glucocorticoids in an attempt to detect this interaction of corticoids and GH. The aim of the present study was to determine the relationship between GH and cortisol spontaneous secretion in children under physiological conditions.

Nine children aged 7.5-13.5 years with different growth rates were evaluated over a 24-hour period. Four were of normal stature (+/- 2 SD) and five were below 2 SD (familial or constitutional short stature). Blood samples were obtained at 20-minute intervals over a 24-hour period.

GH and cortisol concentrations were measured by radioimmunoassay in each of the 73 samples collected.

A significant correlation was obtained between mean 24-hour cortisol concentration and mean 24-hour GH concentration (r = 0.83; P < 0.01), the sum of 24-hour GH pulse amplitudes (r = 0.85; P < 0.01) and the highest 24-hour GH concentration (r = 0.88; P < 0.01). A significant positive correlation was also detected between mean 24-hour cortisol concentration and the number of GH pulses over a 24-hour period (r = 0.70; P < 0.05). However, there was no significant correlation between mean 24-hour GH concentration and number of cortisol pulses over a 24-hour period. The correlation between number of cortisol pulses and number of GH pulses was also non-significant.

These data suggest an interplay of spontaneous GH and cortisol secretion in children. Physiological plasma cortisol levels may play a role in brain-pituitary regulatory mechanisms of GH secretion.