Anterior pituitary function in Cushing's syndrome: study of 36 patients

Clinical Parameters to Distinguish Silent Corticotroph Adenomas from Other Nonfunctioning Pituitary Adenomas

BACKGROUND

It is difficult to distinguish silent corticotroph adenomas (SCAs) from other nonfunctioning pituitary adenomas (NFPAs) preoperatively. This study aimed to determine the preoperative clinical parameters associated with SCAs.

METHODS

This was a retrospective single-center study of patients who underwent surgery for NFPAs during 2011-2016 in our tertiary hospital and who had preoperative combined pituitary function test (CPFT) and immunohistochemical staining results available. After we excluded patients with increased 24-hour urinary free cortisol to preclude overt Cushing's disease, 341 patients were finally enrolled. The medical records, including the CPFT and immunohistochemistry results, of the patients were reviewed.

RESULTS

The age and tumor size were similar between patients with SCAs and other NFPAs. The SCA group had a greater proportion of women (89.2% vs. 57.6%, P < 0.001), cavernous sinus invasion (35.1% vs. 20.7%, P = 0.047), and intratumoral hemorrhage on preoperative sella magnetic resonance imaging (32.4% vs. 9.2%, P < 0.001) compared with the NFPA group. In the preoperative CPFT, the cortisol response was not significantly different between groups. However, the peak adrenocorticotropic hormone (ACTH) (67.80 ± 49.83 vs. 85.67 ± 78.97 pg/mL, P = 0.061) tended to be lower, and the ΔACTH (53.71 ± 50.14 vs. 72.67 ± 75.82 pg/mL, P = 0.046) was significantly lower in SCAs. After we excluded patients with preoperative hypopituitarism caused by mass effects, the peak ACTH (69.39 ± 39.45 vs. 119.75 ± 89.84 pg/mL, P = 0.001) and ΔACTH (58.58 ± 36.51 vs. 107.66 ± 86.05 pg/mL, P = 0.001) were significantly lower in SCAs than in other NFPAs.

CONCLUSIONS

Female sex, cavernous sinus invasion, intratumoral hemorrhage on sella magnetic resonance imaging, and decreased ACTH response in the CPFT are independent indicators of SCAs.

Role of estradiol in cortisol-induced reduction of luteinizing hormone pulse frequency

Precise control of pulsatile GnRH and LH release is imperative to ovarian cyclicity but is vulnerable to environmental perturbations, like stress. In sheep, a sustained (29 h) increase in plasma cortisol to a level observed during stress profoundly reduces GnRH pulse frequency in ovariectomized ewes treated with ovarian steroids, whereas shorter infusion (6 h) is ineffective in the absence of ovarian hormones. This study first determined whether the ovarian steroid milieu or duration of exposure is the relevant factor in determining whether cortisol reduces LH pulse frequency. Prolonged (29 h) cortisol infusion did not lower LH pulse frequency in ovariectomized ewes deprived of ovarian hormones, but it did so in ovariectomized ewes treated with estradiol and progesterone to create an artificial estrous cycle, implicating ovarian steroids as the critical factor. Importantly, this effect of cortisol was more pronounced after the simulated preovulatory estradiol rise of the artificial follicular phase. The second experiment examined which component of the ovarian steroid milieu enables cortisol to reduce LH pulse frequency in the artificial follicular phase: prior exposure to progesterone in the luteal phase, low early follicular phase estradiol levels, or the preovulatory estradiol rise. Basal estradiol enabled cortisol to decrease LH pulse frequency, but the response was potentiated by the estradiol rise. These findings lead to the conclusion that ovarian steroids, particularly estradiol, enable cortisol to inhibit LH pulse frequency. Moreover, the results provide new insight into the means by which gonadal steroids, and possibly reproductive status, modulate neuroendocrine responses to stress.

Gonadotropin pulsatility in Cushing's syndrome compared with polycystic ovary syndrome

Many of the presenting features in women with Cushing's syndrome (CS) are similar to those observed for patients with polycystic ovary syndrome (PCOS). The aim of this study was to compare gonadotropin pulsatility characteristics in CS and PCOS. We evaluated 32 females divided into three groups. The first group comprised 12 females with clinically and biochemically proven CS, subsequently confirmed by histology (seven with Cushing's syndrome, five with adrenal adenoma). The second group comprised ten females with clinical, endocrine and ultrasonographic parameters for PCOS, while the third group comprised ten healthy females with regular menstrual cycles to serve as controls. Blood samples were taken at 15-min intervals for 6 h in the follicular phase, for determination of luteinizing hormone (LH) and follicle-stimulation hormone (FSH). Pulse analysis was carried out using the PulsDetekt program, and statistical analysis was done using the Kruskal-Wallis test. The following data, presented as median (minimum-maximum), were found for the three groups respectively. Number of LH pulses: 0 (0-5), 7 (3-8) and 3 (2-7); LH pulse amplitude: 2.29 (1.98-3.49), 2.27 (1.15-5.90) and 2.03 (1.02-4.46) mU/l; LH pulse mass: 17.81 (14.82-26.20), 29.85 (8.59-185.82) and 27.57 (7.63-66.69) mU/l x min. Number of FSH pulses: 3 (0-3), 2 (0-5) and 3 (1-5); FSH pulse amplitude: 1.62 (1.29-1.94), 1.49 (1.19-4.40) and 2.02 (1.37-2.52) mU/l; FSH pulse mass: 12.17 (9.64-41.69), 11.18 (8.92-33.02) and 15.16 (10.31-18.93) mU/l x min. Only the number of pulses was compared because other parameters of pulsatile secretion cannot be estimated when no pulses are detected. The difference in number of LH pulses between groups was statistically significant (p < 0.05); however, there was no difference in the number of detected FSH pulses between groups (p > 0.05). Attenuation of pulsatile LH secretion indicating gonadotropin deficiency in the majority of women with CS is mostly due to alterations in serum cortisol levels. Our data also suggest that different mechanisms alter LH pulsatile secretion in CS and PCOS.

Cushing's syndrome manifesting as pseudo-central hypothyroidism and hyperosmolar diabetic coma

OBJECTIVE

To report an unusual case of Cushing's syndrome caused by an adrenal pheochromocytoma, manifesting as pseudo-central hypothyroidism and diabetic hyperosmolar coma.

METHODS

A detailed case report is presented, including clinical, laboratory, and radiologic findings as well as results of selective adrenal vein sampling.

RESULTS

In a 69-year-old woman with weight gain and hypothyroidism, diabetes mellitus with hyperosmolar coma developed precipitously. She had mild hypertension, but no diabetes was noted 2 weeks before the hyperosmolar event. Evaluation revealed Cushing's syndrome due to ectopic secretion of adrenocorticotropic hormone from an adrenal pheochromocytoma. After surgical resection of the tumor, the diabetes and the hypertension resolved. Furthermore, the pseudo-central hypothyroidism was eliminated, but primary hypothyroidism was unmasked. This combination has not been reported previously.

CONCLUSION

This case illustrates the array of endocrinopathies that can be associated with pheochromocytoma, causing Cushing's syndrome.

Menstrual abnormalities in women with Cushing's disease are correlated with hypercortisolemia rather than raised circulating androgen levels

Menstrual irregularity is a common complaint at presentation in women with Cushing's syndrome, although the etiology has been little studied. We have assessed 45 female patients (median age, 32 yr; range, 16-41 yr) with newly diagnosed pituitary-dependent Cushing's syndrome. Patients were subdivided into 4 groups according to the duration of their menstrual cycle: normal cycles (NC; 26-30 days), oligomenorrhea (OL; 31-120 days), amenorrhea (AM; > 120 days), and polymenorrhea (PM; < 26 days). Blood was taken at 0900 h for measurement of LH, FSH, PRL, testosterone, androstenedione, dehydroepiandrosterone sulfate, estradiol (E2), sex hormone-binding globulin (SHBG), and ACTH; cortisol was sampled at 0900, 1800, and 2400 h. The LH and FSH responses to 100 micrograms GnRH were analyzed in 23 patients. Statistical analysis was performed using the nonparametric Mann-Whitney U and Spearman tests. Only 9 patients had NC (20%), 14 had OL (31.1%), 15 had AM (33.3%), and 4 had PM (8.8%), whereas 3 had variable cycles (6.7%). By group, AM patients had lower serum E2 levels (median, 110 pmol/L) than OL patients (225 pmol/L; P < 0.05) or NC patients (279 pmol/L; P < 0.05), and higher serum cortisol levels at 0900 h (800 vs. 602 and 580 nmol/L, respectively; P < 0.05) and 1800 h (816 vs. 557 and 523 nmol/L, respectively; P < 0.05) and higher mean values from 6 samples obtained through the day (753 vs. 491 and 459 nmol/L, respectively; P < 0.05). For the whole group of patients there was a negative correlation between serum E2 and cortisol at 0900 h (r = -0.50; P < 0.01) and 1800 h (r = -0.56; P < 0.01) and with mean cortisol (r = -0.46; P < 0.05). No significant correlation was found between any serum androgen and E2 or cortisol. The LH response to GnRH was normal in 43.5% of the patients, exaggerated in 52.1%, and decreased in 4.4%, but there were no significant differences among the menstrual groups. No differences were found in any other parameter. In summary, in our study 80% of patients with Cushing's syndrome had menstrual irregularity, and this was most closely related to serum cortisol rather than to circulating androgens. Patients with AM had higher levels of cortisol and lower levels of E2, while the GnRH response was either normal or exaggerated. Our data suggest that the menstrual irregularity in Cushing's disease appears to be the result of hypercortisolemic inhibition of gonadotropin release acting at a hypothalamic level, rather than raised circulating androgen levels.

Anterior pituitary function after adrenalectomy in patients with Cushing's syndrome

We assessed anterior pituitary function in five patients with Cushing's syndrome before and after the removal of cortisol-secreting adrenal adenomas. Before surgery, all patients lacked response of growth hormone to hypoglycaemia, four had low responses of thyrotrophin to thyrotrophin releasing hormone, three had hypogonadism and two had low prolactin reserve. After successful removal of the adrenal adenoma, all patients developed postoperative hypoadrenocorticism and recovered all impaired anterior pituitary hormones within a period of 3 months. Our results point to a direct inhibiting action of glucocorticoids at the pituitary level as the explanation for the impaired anterior pituitary function. Moreover, direct gonadal suppression by glucocorticoids may be an additional mechanism of hypogonadism in some patients.