Plasma levels of alpha-melanotropin and ACTH-like immunoreactivities do not vary by season or skin type in women from southern and central Europe.

Melanotropins (MSH) are involved in tanning by stimulating melanocytes via the activation of the melanocortin-1 receptor to melanin production. Its main site of production is the pituitary gland, but alpha-MSH and related ACTH peptides are produced at other sites, including the skin. It has been hypothesized that systemic levels of alpha-MSH are controlled by a varying UV radiation (UVR) exposure. A seasonal rhythm of plasma levels has been proposed by some authors. We investigated healthy females in southern Spain and central Austria in summer and winter. The alpha-MSH and ACTH-like immunoreactivity plasma levels did not present marked differences between the groups of Malaga and Linz, dark and light skin and between seasons. An association of alpha-MSH to ACTH or cortisol levels could not be observed. Individual values of alpha-MSH were shown to be relatively constant at both times of measurement (p<0.05 by rank correlation) indicating an independent personal disposition for individual systemic alpha-MSH immunoreactivity levels. Our data do not support the concept of a marked involvement of melanotropins of pituitary origin in tanning, and no seasonal rhythm was observed.