Plasma immunoreactive beta-melanocyte stimulating hormone (lipotropin) levels in individuals with Prader-Labhart-Willi syndrome.

Plasma immunoreactive beta-melanocyte-stimulating hormone (beta-MSH) levels, which actually represent the combined concentrations of beta-lipotropin (beta-LPH) and gamma-LPH in normal individuals, were measured in 12 patients (6 males and 6 females with an average age of 16.8 years, range 4 months to 27 years) with the Prader-Labhart-Willi syndrome (PLWS). Five patients were previously identified with high-resolution analysis as having the 15q chromosomal deletion, whereas 7 patients had normal chromosomes. Hypopigmentation was observed in all 5 patients with the 15q deletion. Of the 7 individuals with normal chromosomes, two were hypopigmented and 5 had normal pigmentation. Fasting (6 to 12 hours) plasma samples were analyzed for immunoreactive beta-MSH in the 12 PLWS individuals. Plasma immunoreactive beta-MSH (LPH) levels were within the normal range in all 12 individuals. There was no significant difference in the plasma immunoreactive beta-MSH concentrations between patients who did and did not have the chromosomal deletion or in those who were or were not hypopigmented. Thus, a decrease in circulating plasma immunoreactive beta-MSH (LPH) does not appear to be the cause of the hypopigmentation observed in some patients with PLWS.