Evidence for a sex difference in the basal growth hormone response to GABAergic stimulation in humans

Evidence has been provided supporting the existence of a sex-related difference in the GH secretion following different GH-releasing stimuli. Since pharmacological activation of the endogenous gammaaminobutyric acid (GABA) system results in increased basal GH release in humans, the present study was undertaken to investigate whether a sex difference is present in the GH response to GABAergic stimulation. Sixteen healthy subjects (8 women and 8 men) received orally 10 mg of baclofen, the direct GABAB agonist which freely crosses the blood-brain barrier. Blood samples were collected before (T = -30 and 0) and 30, 60, 90, 120 and 180 min after the drug administration for plasma GH measurements. Following baclofen administration, plasma GH rose in healthy males (F = 19.417, P less than 0.0001), but not in females (F = 1.67, NS). These results suggest that GABA modulation of human GH release is sex-dependent.