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We assessed the need for continued glucocorticoid replacement therapy in postsurgical pituitary tumor patients using a dexamethasone-ACTH test. The patients received 1 mg dexamethasone, orally, at 2300 h and 250 micrograms synthetic ACTH (Cosyntropin), iv, at 0800 h the next morning. The mean +/- SD integrated cortisol response for a 2-h period of the 31 pituitary tumor patients [1264 +/- 924 micrograms X min/dl (34.87 +/- 25.49 mumol X min/liter)] was significantly less (P less than 0.005) than that of 25 normal subjects [3331 +/- 544 micrograms X min/dl (91.90 +/- 17.04 mumol X min/liter)]. Replacement glucocorticoids were abruptly discontinued in 11 patients with responses above 1450 micrograms X min/dl (40.01 mumol X min/liter). No clinical or laboratory evidence of adrenal insufficiency occurred as long as 15 months after discontinuation. Metyrapone tests, however, in the 11 glucocorticoid-withdrawn patients revealed a reduced mean +/- SD serum 11-deoxycortisol level compared with that of 10 normal subjects [8.9 +/- 4.7 vs. 15.6 +/- 5.0 micrograms/dl (0.26 +/- 0.13 vs. 0.45 +/- 0.16 mumol/liter); P less than 0.005]. Our results indicate that the dexamethasone-ACTH test is useful in identifying patients in whom replacement glucocorticoid therapy can be safely withdrawn under nonstressed conditions. The test can be simplified to one plasma cortisol level determined 30 min after ACTH administration.

In an attempt to develop a model relating several clinical indices of thyroid hormone action to serum free T3 concentration and the estimated occupancy of nuclear T3 receptors, we have performed serial studies in 19 patients with hyperthyroidism and 16 patients with hypothyroidism both before and after the initiation of standard treatment. With increasing serum free T3 concentrations, we observed gradual increases in mean heart rate and sleeping heart rate, reaching, respectively, mean plateau values of 109 and 99 beats/min. As expected, with increasing serum T3 concentrations, a hyperbolic fall in serum cholesterol, serum creatine phosphokinase activity (CPK), and Achilles tendon reflex relaxation time (ATRT) was noted. Nuclear occupancy was calculated from the plasma T3 concentration and the physicochemical characteristics of human nuclear receptor sites, as determined in other studies. Nuclear T3 occupancy was found to be linearly related to mean heart rate (r = 0.81) and to sleeping heart ra...