Effect of metoclopramide-A dopaminergic blocker and endogenous cortisol on TSH secretion in critically ill men

: In 17 critically ill men, low levels of FT4, TT4, TT3 and elevated levels of rT3 and cortisol were found. In spite of the low levels of circulating thyroid hormones, TSH levels of the critically ill men were significantly lower than those of the control group, with no correlations to the high cortisol levels. After iv injection of metoclopramide (MCP), a dopamine (DA) receptor blocker, the TSH and prolactin (Prl) increments in the critically ill patients were significantly lower than in the controls. No correlation was observed between basal cortisol levels and integrated TSH response to MCP. It is suggested that increased DA tone or high cortisol levels are not responsible for the lower basal TSH levels and for the blunted TSH or Prl responses to MCP in the critically ill. High levels of cortisol may be responsible for the altered TT4 peripheral metabolism to TT3 and rT3 in these patients.