Abstract
Since the discovery, isolation and purification of GHRH in 1982, its potential role in the diagnosis of growth hormone (GH) insufficiency has been unclear. The doses of GHRH administered have varied greatly. Supramaximal somatotroph stimulation and release of various GH pools may account for variation in results within and between individuals. We have investigated the GH response to low-dose GHRH (1-29)NH2, doses 0.5-10mcg,in 5 adult male volunteers (mean weight 84kg) with subsequent GH sampling at 5 minute intervals for 1 hour post-administration. The ED50 calculated from the dose-response curve was 7.8mcg GHRH corresponding to a dose of 0.09mcg/kg. Adequate GH peaks above our unit's “cut-off” value of 13mU/l were obtained with a GHRH dose of 8.5mcg (0.1mcg/kg). Whilst all GH peaks were identified within 30 minutes of GHRH administration, none were detected before 10 minutes and the mode of the distribution was 15 minutes. Maximal somatotroph stimulation occurred at a dose of 10mcg (0.12mcg/kg). Higher GHRH dosage altered the timing of the initial GH peak and the subsequent clearance time of circulating GH. We conclude that a dose of 0.1mcg/kg GHRH(1-29)NH2 is sufficient to produce “normal” GH values. This dose is a ten-fold decrease in comparison with current recommended protocols. The low-dose GHRH stimulation test probably represents a more physiological test of the readily releasable GH store than other tests which incorporate larger GHRH doses.
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Winrow, A., Spoudeas, H., Pringle, P. et al. THE LOW-DOSE GROWTH HORMONE RELEASING HORMONE (GHRH) STIMULATION TEST. Pediatr Res 33 (Suppl 5), S26 (1993). https://doi.org/10.1203/00006450-199305001-00140
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DOI: https://doi.org/10.1203/00006450-199305001-00140