Impaired sensitivity of the hypothalamo-pituitary-thyroid axis to the suppressant effect of dexamethasone in elderly subjects.
It has been shown that glucocorticoids have a suppressant effect on the thyrotropin (TSH) response to thyrotropin-releasing hormone (TRH) in young men. To assess whether this effect of corticosteroids is also present in aged individuals, six young subjects (aged 26-32 years) and six elderly men (aged 68-75 years) underwent, in random order, at 1 week intervals, three TRH stimulation tests 30 min after IV administration of placebo and 2 mg and 4 mg dexamethasone phosphate. Elderly men showed higher basal plasma levels of TSH (P less than 0.02) and lower plasma levels of FT3 (P less than 0.03) and FT4 (P less than 0.01). The TSH response to TRH was significantly lower in aged subjects than in young ones (P less than 0.009). Moreover, 2 mg dexamethasone significantly blunted the TSH response to TRH in young men (P less than 0.0001), but not in the elders. The inhibitory effect of the glucocorticoid on the TRH-induced TSH secretion, in aged subjects, was evident only after 4 mg dexamethasone administration (P less than 0.0001). These data confirm that glucocorticoids have an inhibitory role on the thyrotropic axis and show, for the first time, that normal elderly men are hyporesponsive to this suppressant effect of corticosteroids.
Iovino
M
M
Department of Neurology, 2nd Medical School, University of Naples, Italy.
Steardo
L
L
Monteleone
P
P
D000328:Adult; D000368:Aged; D000375:Aging / Q000097:blood / Q000502:physiology*; D000704:Analysis of Variance; D003907:Dexamethasone / Q000494:pharmacology*; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects*; D008297:Male; D010913:Pituitary-Adrenal System / Q000187:drug effects*; D012016:Reference Values; D013961:Thyroid Gland / Q000187:drug effects*; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D003907:Dexamethasone; D013972:Thyrotropin; D013974:Thyroxine