Impairment of growth hormone responsiveness to growth hormone releasing hormone and pyridostigmine in patients affected by Prader-Labhardt-Willi syndrome.

In order to evaluate the impairment of GH response in patients affected by Prader-Labhardt-Willi (PLW) syndrome, in 18 patients we studied GH response to clonidine and to GHRH + pyridostigmine, a cholinergic drug which enhances GHRH induced GH responsiveness in obese patients. After clonidine GH response was abnormal in 14/18 subjects (mean GH peak: 4.1 +/- 1.3 micrograms/l; area under curve: 208.1 +/- 74.2 micrograms/l.h) while all but 5 patients showed an inadequate GH response to GHRH + pyridostigmine (mean GH peak: 13.4 +/- 2.5 micrograms/l; area under curve: 903.4 +/- 171.0 micrograms/l.h). However, in the three patients with low adiposity index, GH response to GHRH + pyridostigmine was significantly higher than that observed in fatter subjects. In addition, GH response to GHRH + pyridostigmine was negatively correlated to age and adiposity index. In conclusion, our data are consistent with the hypothesis of the existence of a complex derangement of GH neuroendocrine regulation in these subjects.