Are cadmium effects on plasma gonadotropins, prolactin, ACTH, GH and TSH levels, dose-dependent?

It is well established that cadmium affects plasma levels of the pituitary hormones studied. However, whether the effects of the metal are dose dependent needs to be clarify. This work was designed to evaluate the possible changes in plasma levels of gonadotropins, prolactin, ACTH, GH and TSH after oral cadmium exposure in adult male rats. Plasma levels of these hormones were measured in adult male rats exposed to cadmium chloride (CdCl2) in the drinking water at the doses of 5, 10, 25, 50 or 100 ppm for one month. The lower dose of cadmium increased plasma prolactin levels and higher doses of the metal (25 or 50 ppm) decreased them. There was a continuous increase of plasma ACTH levels from the lower to 25 ppm dose of CdCl2 and decreased them after to basal values with the highest dose. Plasma GH levels were increased with the dose of cadmium of 10 ppm, although the doses of 5, 25 and 50 ppm decreased them. Plasma LH levels were only reduced with the dose of 50 ppm of CdCl2, whereas those of FSH increased. Plasma TSH levels were increased with the doses of 5, 25 and 100 ppm of CdCl2. Cadmium concentration increased in pituitary with the doses of 125, 50 and 100 ppm of CdCl2. These data suggest that cadmium differentially affects the secretory mechanisms of the pituitary hormones studied depending on the dose used. The effects of the metal on prolactin and ACTH are dose-dependent.