A B S T R A C T Synthetic ovine corticotropin-releasing factor (CRF) was administered to normal male volunteer subjects as an intravenous bolus or 30-s infusion. Doses of CRF ranging from 0.001 to 30 sg/kg body wt were administered, and plasma immunoreactive (IR)-ACTH and IR-cortisol concentrations were measured. The threshold dose appeared to be 0.01-0.03 ag/kg, the half-maximal dose 0.3-1 sg/kg, and the maximally effective dose 3-10 ug/kg. Basal concentrations of IR-ACTH and IR-cortisol were 14±7.6 pg/ ml (mean±SD) and 5.6±2.2 gg/dl, respectively. IR-ACTH rose as early as 2 min after CRF injection, reached peak levels in 10-15 min, and declined slowly thereafter. IR-cortisol rose at 10 min or later and reached peak levels in 30-60 min. At a dose of 30 jig/ kg, neither IR-ACTH nor IR-cortisol fell from peak levels of 82±21 pg/ml (mean±SE) and 23±1.4 ,g/dl, respectively, during the 2-h course of the experiment, indicating that CRF has a sustained effect on ACTH release and/or a prolonged circulating plasma halflife. There was little or no increase in the levels of other anterior pituitary hormones. At doses of 1 gg/ Preliminary results of these studies were presented by Dr.
A bstract. Arginine vasopressin (AVP) stimulates ACTH release in man and acts synergistically with synthetic ovine corticotropin-releasing factor (oCRF) in vitro. This study was designed to examine in man the combined effects of synthetic AVP (10 U intramuscularly) and oCRF (1 gg/kg intravenously) on ACTH release.Five normal male volunteers participated in five separate experiments: (a) AVP alone; (b) oCRF alone; (c) AVP followed by oCRF 15 min later; (d) simultaneous AVP and oCRF; and (e) insulin-induced hypoglycemia. Plasma immunoreactive ACTH (IR-ACTH) and IR-cortisol were measured for 4 h after injection of each hormone; basal levels for all subjects were .9±1.2 pg/ml and 4. 9±0.4 ,gg/dl (mean±SE), respectively. AVP and oCRF, when given individually, caused rapid rises in IR-ACTH to similar peak levels of 25±6.6 and 33±4.6 pg/ml, respectively. AVP given 15 min before oCRF caused a 2.6-fold potentiation ofthe oCRF response, with a peak IR-ACTH of 85±4.6 pg/ml. AVP given at the same time as oCRF produced a fourfold potentiation of the peak IR-ACTH response to 132±11 pg/ml. These ACTH responses were far greater than those previously observed after 30-fold greater doses of oCRF alone. By way of comparison, insulin-induced hypoglycemia caused a peak IR-ACTH of 169±20 pg/ml. IR-ACTH returned to base line at 60-90 min after AVP alone, whereas the prolonged effect of oCRF was apparent whether it was given alone or in combination with AVP. The mean peak IR-cortisol responses to AVP, oCRF, and AVP given 15 min before oCRF were similar (16.5±0.9, 16.4±2.3, and 18.5±0.8 ,ug/dl, respectively), but the peak IR-cortisol responses to AVP and oCRF given simultaneously and to insulininduced hypoglycemia were 1.5 and 1.7 times greater, respectively. IR-cortisol returned to base line within 2-3 h after AVP alone, but remained elevated for at least 4 h after oCRF alone or in combination with AVP. These results indicate that AVP acts synergistically with oCRF to release ACTH in man and suggest that AVP may play a physiologic role in modulating the ACTH response mediated by corticotropin-releasing factor.
Corticotropin-releasing factor (CRF) was administered as an iv bolus to two young women with mild Cushing's disease shortly before and one week after successful transsphenoidal microadenomectomy. The dose of CRF (1 microgram/kg body weight) had previously been shown to stimulate increased plasma ACTH and cortisol in normal subjects. In the first patient, prior to surgery, there were brisk increases in ACTH and cortisol that exceeded those observed in normal subjects. ACTH rose by 2 min and reached a peak between 15-30 min. Cortisol increased by 10 min and peaked between 45-60 min. After surgery, at a time when plasma cortisol was maintained at similar levels with exogenous hydrocortisone, there was no plasma ACTH or LH, TSH and prolactin increased after administration of LRH and TRH, and GH increased in response to insulin-induced hypoglycemia. The second patient had higher basal plasma ACTH and cortisol than the first patient. CRF-induced increments in ACTH and cortisol were much less, but the time course was similar and peak levels attained were still higher than those in normal subjects. After surgery, at a time when plasma cortisol was maintained at a much lower level with exogenous hydrocortisone, there was no plasma ACTH or cortisol response. She had mild, transient diabetes insipidus. Basal levels of all other anterior pituitary hormones were normal. These results demonstrate that two microadenomas causing Cushing's disease were responsive to CRF in situ and suggest that CRF may be involved in the etiology and/or the responses to changes in plasma glucocorticoid concentrations observed in patients with Cushing's disease.
Men have lower high density lipoprotein (HDL) and higher low density lipoprotein (LDL) levels than women. To dynamically evaluate the role of endogenous testosterone on the lipoprotein profile, eight normal men received a long-acting gonadotropin releasing hormone analog (LHRHA) for 10 weeks by SC injection. Plasma testosterone levels were acutely lowered below 1 ng/ml after 4 weeks of LHRHA treatment and remained depressed at this level for the duration of administration of the analog. There were prompt increases in total cholesterol [baseline vs. peak (milligrams per dl) mean +/- SEM, 177 +/- 18 vs. 208 +/- 22; P less than 0.005], apoprotein B (apo B; 69 +/- 12 vs. 97 +/- 13; P less than 0.05), HDL-cholesterol (23 +/- 2 vs. 33 +/- 2; P less than 0.005), and apo A-I (80 +/- 7 vs. 112 +/- 5; P less than 0.005), but not in apo A-II (40 +/- 3 vs. 40 +/- 4; P = NS) levels. The peaks occurred after 10 weeks of treatment and were followed by a fall in these values after discontinuing LHRHA. These changes were largely prevented in a second study (six men) in which LHRHA was administered together with im testosterone enanthate, which was given every 2 weeks. These results show that suppression of endogenous testosterone leads to increases in HDL and LDL, demonstrating that testosterone has an important effect on lipoprotein metabolism and plays a key role in defining the lipoprotein profile in men.
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