Anomalies in the hormonal status of athymic nude mice.

The serum levels of hormones that are known to influence growth, development, and differentiation of the skin and its appendages were analyzed in female haired (NMRI) and nude (NMRI, nu/nu) mice. Whereas the concentrations of testosterone, prolactin, and triiodothyronine did not differ in nude animals from those found in normal mice of the same age in the anestrous phase of the sexual cycle, the serum levels of estradiol, progesterone, and thyroxine were found in female nude mice at significantly lower levels than in normally haired animals. These results point to a hormonal situation that contributes to the poor fertility of homozygous (nu/nu) female mice and may promote impairment of growth and differentiation of skin and hair, resulting in the macroscopic nudity of athymic, nude mice.