Effects of short- and long-duration hypothyroidism on hypothalamic-pituitary-adrenal axis function in rats: in vitro and in situ studies.

The purpose of this study is to assess the effects of hypothyroidism on the hypothalamic-pituitary-adrenal (HPA) axis; the functional integrity of each component of the HPA axis was examined in short-term and long-term hypothyroidism. Neuropeptide synthesis, release, and content were evaluated in vitro both in the hypothalamus and anterior pituitary, and corticosterone release was assessed in primary adrenal cell cultures at 7 (short-term) and 60 days (long-term hypothyroidism) after thyroidectomy in male rats. Hypothyroid rats showed adrenal insufficiency in several parameters, which were associated with the duration of hypothyroidism.