Role of local 11 beta-hydroxysteroid dehydrogenase type 2 expression in determining the phenotype of adrenal adenomas.

It is not understood why some adrenal adenomas are nonfunctional and others with similar histopathology cause preclinical or overt Cushing's syndrome. Two isozymes of 11 beta-hydroxysteroid dehydrogenase, types 1 and 2 (HSD11B1 and HSD11B2), are known to modulate glucocorticoid levels in other tissues and might influence circulating levels of active and inactive glucocorticoids if they were expressed in adrenal adenomas. We determined levels of expression of these isozymes in normal adrenals and 61 adrenal adenomas by quantitative competitive RT-PCR and immunohistochemistry. There were no differences in HSD11B1 mRNA levels among adrenal tumor groups. HSD11B2 mRNA levels were high in nonfunctioning adenomas and preclinical Cushing's adenomas compared with levels in control adrenals or in adenomas causing overt Cushing's syndrome. HSD11B2 immunoreactivity was not detected in control adrenals, but was observed in more than half of these tumors. When nonfunctioning adenomas and those causing preclinical and overt Cushing's syndrome were considered as a single group, HSD11B2 mRNA levels were strongly correlated with the ratio of plasma cortisone to cortisol, and a simple model incorporating adrenal HSD11B2 expression and tumor size as variables could predict more than 50% of the interindividual variation in plasma cortisol levels (r(2) = 0.54; P < 0.0001). Adrenal HSD11B2 may regulate levels of active and inactive glucocorticoids in the systemic circulation under these conditions, presumably by acting in an autocrine or paracrine manner. Nonfunctioning adenomas and those causing preclinical and overt Cushing's syndrome may represent a continuum with clinical manifestations depending mainly on tumor size and HSD11B2 expression levels.

Glycyrrhizic acid suppresses type 2 11 beta-hydroxysteroid dehydrogenase expression in vivo.

Licorice-derivatives such as glycyrrhizic acid (GA) competitively inhibit 11 beta-hydroxysteroid dehydrogenase(11 beta-HSD) type 2 (11-HSD2) enzymatic activity, and chronic clinical use often results in pseudoaldosteronism. Since the effect of GA on 11-HSD2 expression remains unknown, we undertook in vivo and in vitro studies. Male Wistar rats were given 30, 60 or 120 mg/kg of GA twice a day for 2 weeks. Plasma corticosterone was decreased in those given the 120 mg dose, while urinary corticosterone excretion was increased in those given the 30 and 60 mg doses but decreased in those given 120 mg GA. NAD(+)-dependent dehydrogenase activity in kidney microsomal fraction was decreased in animals receiving doses of 60 and 120 mg GA. The 11-HSD2 protein and mRNA levels were decreased in those given 120 mg GA. In contrast, in vitro studies using mouse kidney M1 cells revealed that 24h treatment with glycyrrhetinic acid did not affect the 11-HSD2 mRNA expression levels. Thus, in addition to its role as a competitive inhibitor of 11-HSD2, the chronic high dose of GA suppresses mRNA and protein expression of 11-HSD2 possibly via indirect mechanisms. These effects may explain the prolonged symptoms after cessation of GA administration in some pseudoaldosteronism patients.

Transient Graves disease developing after surgery for Cushing disease.

A 49-year-old man, diagnosed as having Cushing disease in 1976 at the age of 26, underwent a Hardy operation 13 years after treatment with reserpine combined with pituitary radiation. In laboratory examinations before and 2 weeks after the successful surgery, the patient's serum thyroid hormones were found to be normal except for suppressed serum thyroid-stimulating hormone (TSH), and his serum anti-TSH receptor (TRAb) and anti-TSH receptor-stimulating antibodies (TSAb) were negative. Glucocorticoid supplemental treatment was withdrawn on the 15th day after surgery and was restarted on the 48th day, during which time there were no signs of an adrenal crisis. Sinus tachycardia, fine finger tremor, and enlarged thyroid gland, approximately the size of a thumb head, were observed on the 140th day after surgery. Thyrotoxicosis with increased serum TSAb and TRAb and high 24-h thyroid uptake of 123I was noted, indicating a diagnosis of Graves disease. No special treatment was prescribed, but his serum thyroid hormone levels started to decrease on the 140th day after the operation and returned to normal on the 520th day. Serum TRAb also spontaneously decreased, but the timing of the peak of serum TRAb was delayed 230 days from that of the thyroid hormones. This is the first reported case of Graves disease after successful surgery for Cushing disease. We presume that a latent autoimmune process in the thyroid, suppressed by hypercortisolism, developed into overt Graves disease after the abrupt reduction of plasma glucocorticoid levels induced by surgery.

Altered corticosteroid metabolism differentially affects pituitary corticotropin response.

To evaluate the effects of altered corticosteroid metabolism on the hypothalamic-pituitary-adrenal axis, we examined rats treated with glycyrrhizic acid (G rats) or rifampicin (R rats) for 7 days. The half-life of exogenously administered hydrocortisone as a substitute for corticosterone was longer in G rats and shorter in R rats, with no differences in basal plasma levels of ACTH or corticosterone. The ACTH responses to human corticotropin-releasing factor (CRF) or insulin-induced hypoglycemia were greater in G rats and tended to be smaller in R rats compared with those in the control rats, whereas the corticosterone response was similar. No difference was observed in the content and mRNA level of hypothalamic CRF among the groups. The number and mRNA level of CRF receptor and type 1 11 beta-hydroxysteroid dehydrogenase (11-HSD1) mRNA level in the pituitary were increased in G rats but not changed in R rats, suggesting that chronically increased intrapituitary corticosterone upregulates pituitary CRF receptor expression. In contrast, CRF mRNA levels in the pituitary were increased in R rats. Our data indicate novel mechanisms of corticosteroid metabolic modulation and the involvement of pituitary 11-HSD1 and CRF in glucocorticoid feedback physiology.