Modulation of central glucocorticoid receptors in short- and long-term experimental hyperthyroidism.

Hyperthyroidism is associated with a significant increase in circulating glucocorticoid levels and hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis. The aim of this study was to examine whether the HPA axis hyperactivity observed in hyperthyroidism may be explained by a disturbed feedback inhibition of endogenous glucocorticoids through two specific intracellular receptors in the brain: the high affinity mineralocorticoid receptor (MR) and the lower affinity glucocorticoid receptor (GR). Cytosolic receptor binding and gene expression was assessed in rats with short (7 days) and long standing (60 days) eu- and hyperthyroidism.

Effects of experimentally induced hyperthyroidism on central hypothalamic-pituitary-adrenal axis function in rats: in vitro and in situ studies.

Hyperthyroidism is associated with hypercorticosteronemia, although the locus that is principally responsible for the hypercorticosteronism remains unclear. The purpose of this study was to assess the effects of hyperthyroidism on the functional integrity of the hypothalamic-pituitary-adrenal (HPA) axis, to identify the locus in the HPA axis that is principally affected, and address the time-dependent effects of alterations in thyroid status. The functional integrity of each component of the HPA axis was examined in vitro and in situ in sham-thyroidectomized male Sprague-Dawley rats given placebo or in thyroidectomized rats given pharmacological dose (50 μg) of thyroxin for 7 or 60 days.

Effects of short- and long-duration hypothyroidism on function of the rat hypothalamic-pituitary-adrenal axis.

The effects of hypothyroidism on the functional integrity of the hypothalamic-pituitary-adrenal (HPA) axis were investigated in adult male rats. HPA axis function was examined in vivo in sham-thyroidectomized male Sprague-Dawley rats or in thyroidectomized rats for 7 (short-term hypothyroidism) or 60 (long-term hypothyroidism) days. Peripheral ACTH and corticosterone responses to insulin-induced hypoglycemia and interleukin (IL)-1α stimulation were used to indirectly assess the hypothalamic CRH neuron.

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.

Experimentally-induced hyperthyroidism is associated with activation of the rat hypothalamic-pituitary-adrenal axis.

Objective: Previous studies on the effects of altered thyroid function on the secretion and metabolism of adrenocortical hormones suggest a degree of adrenocortical hyperactivity in hyperthyroidism. We have previously shown that experimentally-induced hyperthyroidism is associated with significant alterations in pituitary-adrenal responsiveness to synthetic ovine corticotropin-releasing hormone (oCRH) that are contingent upon the duration of the altered thyroid function. The purpose of this study was to assess the time-dependent effects of hyperthyroidism on the functional integrity of the hypothalamic-pituitary-adrenal (HPA) axis by in vivo stimulation of the hypothalamic CRH neuron and adrenal cortex.