Coicosteroids suppress: September 2009

Ans. B: ACTHFree glucocoicoids inhibit ACTH secretion, and the degree of pituitary inhibition is propoionate to the circulating glucocoicoid level. The inhibitory effect is exeed at both the pituitary and the hypothalamic levels. The inhibition is due primarily to an action on DNA, and maximal inhibition takes several hours to develop, although more rapid "fast feedback" also occurs. The ACTH-inhibiting activity of the various steroids parallels their glucocoicoid potency. A drop in resting coicoid levels stimulates ACTH secretion, and in chronic adrenal insufficiency the rate of ACTH synthesis and secretion is markedly increased.Thus, the rate of ACTH secretion is determined by two opposing forces: the sum of the neural and possibly other stimuli converging through the hypothalamus to increase ACTH secretion, and the magnitude of the braking action of glucocoicoids on ACTH secretion, which is propoionate to their level in the circulating blood