David N. Orth

Cushing's Syndrome

Cushings syndrome is usually caused by the secretion of corticotropin or cortisol by a pituitary or adrenal tumor, respectively, or by ectopic secretion of corticotropin. It is possible to determine the specific abnormality in most patients, but it can sometimes be difficult to decide whether the patient has hypercortisolism and whether it is primary or due to major depressive disorder or to the stress of other diseases. Determining the cause of the hypercortisolism involves performing multiple tests in a logical sequence; the results should all be consistent with the same diagnosis. Treatment should aim to cure the hypercortisolism and to eliminate any tumor that threatens the patients health, while minimizing the chance of an endocrine deficiency or long-term dependence on medications.

Results of Treatment in 108 Patients with Cushing's Syndrome

Abstract In 17 years, 108 patients with Cushings syndrome were treated at Vanderbilt University. Seventeen had adrenal adenoma, 10 adrenal carcinoma, 17 ectopic ACTH syndrome, and 64 Cushings disease. Surgery for adrenal adenoma was uniformly successful. Three carcinomas were surgically cured, and two patients had remissions; these two and another patient subsequently responded to o.p′DDD. Four cases were not amenable to therapy. No patient with ectopic ACTH syndrome was cured, but some responded metabolically to metyrapone. In Cushings disease, pituitary irradiation cured 10 of 51 patients and improved 13 without complications. All six unilateral adrenalectomies and two of five subtotal adrenalectomies were unsuccessful, but bilateral adrenalectomy (19 cases) was always curative. After o,p′DDD treatment serum cortisol levels returned to normal, without mineralocorticoid deficiency, in eight patients. Thus, except in patients with ectopic ACTH syndrome or adrenal carcinoma, appropriate treatment for Cu...

Effect of synthetic ovine corticotropin-releasing factor. Dose response of plasma adrenocorticotropin and cortisol.

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 micrograms/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 micrograms/kg, the half-maximal dose 0.3-1 micrograms/kg, and the maximally effective dose 3-10 micrograms/kg. Basal concentrations of IR-ACTH and IR-cortisol were 14 +/- 7.6 pg/ml (mean +/- SD) and 5.6 +/- 2.2 micrograms/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 micrograms/kg, neither IR-ACTH nor IR-cortisol fell from peak levels of 82 +/- 21 pg/ml (mean +/- SE) and 23 +/- 1.4 micrograms/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 half-life. There was little or no increase in the levels of other anterior pituitary hormones. At doses of 1 microgram/kg and higher, facial flushing, tachycardia, and, in some subjects, a 15-29-mmHg decline in systemic arterial blood pressure were observed, even though blood volume was replaced and the subjects remained supine. These data indicate that synthetic ovine CRF is a very potent and specific ACTH secretagogue in man. Administered with caution until its vasomotor effects are more fully defined, CRF promises to be a safe and very useful investigative, diagnostic, and, possibly, therapeutic agent in man.

Arginine vasopressin potentiates adrenocorticotropin release induced by ovine corticotropin-releasing factor.

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 micrograms/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 less than or equal to 9 +/- 1.2 pg/ml and 4.9 +/- 0.4 micrograms/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 of the 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 micrograms/dl, respectively), but the peak IR-cortisol responses to AVP and oCRF given simultaneously and to insulin-induced 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.

Results of Treating Childhood Cushing's Disease with Pituitary Irradiation

To determine the usefulness of conventional pituitary irradiation in childhood Cushings disease, we reviewed the results of this treatment in 15 patients. Twelve were cured (mean plasma cortisol of less than 10 microgram per deciliter and 24-hour urinary 17-hydroxycorticosteroid excretion of less than 7 mg per gram of creatinine) within 18 months, and 10 of the 15 were cured within nine months. Three failures required bilateral adrenalectomy. Growth resumed in 12, with adult heights of 156 to 166 cm. Sexual development proceeded normally in all 15, with normal secondary sexual characteristics and sexual function, and demonstrated fertility in four married adults. Intellectual function appeared normal. Basal and stimulated hormone levels were normal, except for subnormal (5 ng per milliliter or less) growth hormone levels after hypoglycemia in one of 12 patients. There were no complications of therapy and no progressive pituitary enlargement or hyperpigmentation. Pituitary irradiation is safe and effective therapy for childhood Cushings disease.

Specific high-affinity binding protein for human corticotropin-releasing hormone in normal human plasma

A protein of Mr 25-40 kilodaltons in normal human plasma binds human corticotropin-releasing hormone (hCRH), but not ovine CRH. Binding requires both N- and C-terminal hCRH sequences and has a Kd of 2 X 10(-10) M and a binding site concentration of 1.4 pmoles per ml of plasma. Its binding is not affected by heating to 56 degrees C for 1 h, but is abolished by exposure to 6 M guanidine-HCl, 10 mM dithiothreitol. Binding proceeds rapidly at 37 degrees C and is 75% complete within 4 min. Neither rat nor sheep plasma appears to contain a CRH-binding protein. CRH-binding protein may explain the brief biological action of hCRH as compared to ovine CRH in man and why high concentrations of plasma immunoreactive hCRH in women during third-trimester pregnancy do not cause increased ACTH secretion.

Individual differences in repressive-defensiveness predict basal salivary cortisol levels.

Prior studies assessing the relation between negative affective traits and cortisol have yielded inconsistent results. Two studies assessed the relation between individual differences in repressive-defensiveness and basal salivary cortisol levels. Experiment 1 assessed midafternoon salivary cortisol levels in men classified as repressors, high-anxious, or low-anxious. In Experiment 2, more rigorous controls were applied as salivary cortisol levels in women and men were assessed at 3 times of day on 3 separate days. In both studies, as hypothesized, repressors and high-anxious participants demonstrated higher basal cortisol levels than low-anxious participants. These findings suggest that both heightened distress and the inhibition of distress may be independently linked to relative elevations in cortisol. Also discussed is the possible mediational role of individual differences in responsivity to, or mobilization for, uncertainty or change.

Normal and abnormal regulation of β-MSH in man

A B S T R A C T The regulation of plasma 8-melanocyte-stimulating hormone (,8-MSH) in man has been studied utilizing a radioimmunoassay previously described (1). In normal subjects plasma p-MSH values ranged from 20 to 110 pg/ml. Metyrapone increased and dexamethasone decreased plasma P-MSH levels. Surgical stress stimulated f-MSH secretion. Plasma P-MSH levels were elevated in patients with untreated Addisons disease and untreated congenital adrenal hyperplasia, and these levels fell to normal during glucocorticoid therapy. In patients with Cushings syndrome due to pituitary adrenocorticotropic hormone (ACTH) excess, plasma fi-MSH was slightly elevated before treatment. In those patients who developed pituitary tumors and hyperpigmentation after bilateral adrenalectomy, plasma P-MSH was greatly elevated. In patients with Cushings syndrome due to adrenal tumor, plasma j9-MSH was subnormal. In patients with the ectopic ACTH syndrome, the levels of plasma f8-MSH were high. Plasma fi-MSH had a diurnal variation in normal subjects, patients with Addisons disease, and patients with congenital adrenal hyperplasia; but the normal diurnal variation was lost in patients with Cushings disease. In patients with high plasma 8-MSH, simultaneous determinations of plasma ACTH showed close correlation between the degree of elevation of ACTH and that of 8-MSH. In extracts of tumors from patients with the ectopic ACTH-MSH syndrome the quantities of the two hormones were roughly equivalent. In patients with hyperpigmentation due to a variety of disorders other than pituitary-adrenal abnormalities, plasma 8-MSH was normal. It is concluded that the secretion of P-MSH is regulated by the same factors that regulate ACTH.

Ectopic ACTH syndrome caused by a bronchial carcinoid tumor responsive to dexamethasone, metyrapone, and corticotropin-releasing factor

Cushings syndrome due to bronchial carcinoid tumors that secrete adrenocorticotropin (ACTH) may be difficult to distinguish from pituitary Cushings disease, since the responses to dexamethasone and metyrapone are sometimes similar. Recently, the ACTH and cortisol responses to ovine corticotropin-releasing factor (oCRF) have been shown to be different in pituitary Cushings disease than in Cushings syndrome due to other causes. It is not known if the response to oCRF can distinguish pituitary Cushings disease from those ACTH-secreting bronchial carcinoid tumors that respond to dexamethasone and metyrapone. A case of Cushings syndrome due to an ACTH-secreting bronchial carcinoid is described in which the responses to dexamethasone, metyrapone, and oCRF were indistinguishable from the responses observed in pituitary Cushings disease. A bronchial carcinoid tumor should be considered even when responses to dexamethasone, metyrapone, and oCRF suggest pituitary Cushings disease.

Radioimmunoassay of β-MSH in Human Plasma and Tissues

: A radioimmunoassay method for beta-melanocyte-stimulating hormone (beta-MSH) has been developed and utilized in the identification and quantification of this hormone in human plasma and tissues. The concentration of beta-MSH in two human pituitary glands was found to be approximately 350 mug/g. beta-MSH was identified in the tumor tissue of all 11 patients with the ectopic ACTH syndrome who were studied; concentrations in individual cases ranged from 3 to 1600 ng/g. In plasma of chronically hyperpigmented patients with Addisons disease, Cushings disease (after bilateral adrenalectomy), and the ectopic ACTH syndrome, beta-MSH concentrations of 0.5-6 ng/ml were found. The degree of clinical hyperpigmentation was well correlated with the quantity of beta-MSH in the plasma. beta-MSH concentrations in the plasma of normal subjects were less than 0.09 ng/ml. In all of these circumstances, bioassays for MSH were also performed, and it was found that most of the biologic MSH activity of the plasma and tissues could be accounted for by beta-MSH.