Growth hormone responses to dexamethasone in healthy females throughout the menstrual cycle

• Published in: Clinical endocrinology (Oxford) Vol. 42; no. 2; p. 173
• Main Authors: Thakore, J H, Dinan, T G
• Format: Journal Article
• Language: English
• Published: England 01.02.1995
• Subjects: Adult; Dexamethasone - pharmacology; Double-Blind Method; Estradiol - blood; Female; Growth Hormone - blood; Humans; Menstrual Cycle - blood; Progesterone - blood; Stimulation, Chemical; Time Factors
• ISSN: 0300-0664
• DOI: 10.1111/j.1365-2265.1995.tb01859.x

In health, acute administration of dexamethasone (DEX) leads to growth hormone release. As sex steroids have a profound influence on the somatotrophic axis, we decided to investigate the effects of DEX on GH release throughout the menstrual cycle. A within subjects, randomized double-blind counter-balanced design was employed. Baseline levels of GH, oestradiol and progesterone were taken at three time points in two consecutive menstrual cycles, after which 4 mg of oral DEX or placebo was administered. Plasma samples for GH estimation were taken at 60, 180, 240 and 300 minutes. Each woman was tested 6 times, 3 times with placebo and 3 times with DEX. Six women with regular menstrual cycles were studied. Plasma GH, oestradiol and progesterone were measured by radioimmunoassay. When expressed as maximum change from base line (delta GH) mean GH responses to DEX increased incrementally from early (12.2 +/- 2.5 mU/l), through mid (25.6 +/- 3.3 mU/l) to late (37.2 +/- 3.5 mU/l) cycle. This represents a significant effect of cycle phase on GH responses to DEX (P < 0.05). GH responses at both the mid-cycle and the luteal time points are different from those during the follicular phase (P < 0.05) and difference between mid-cycle and luteal phases just fail to reach significance (P < 0.15). Responses to placebo did not vary from baseline. Plasma oestradiol values were significantly correlated with GH responsivity to active drug throughout the cycle (P < 0.05); the same was not true of progesterone. Our study has demonstrated that dexamethasone-mediated GH release shows a stepwise increase throughout the menstrual cycle.