Hypothalamic abnormalities in patients with pituitary-dependent Cushing's syndrome

Diurnal Range and Intra-patient Variability of ACTH Is Restored With Remission in Cushing's Disease

CONTEXT

Single ACTH measurements have limited ability to distinguish patients with Cushing's disease (CD) from those in remission or with other conditions.

OBJECTIVE

To investigate the changes in ACTH levels before and after transsphenoidal surgery (TSS) to identify trends that could confirm remission from CD and help establish ACTH cutoffs for targeted clinical trials in CD.

DESIGN

Retrospective analysis of CD patients who underwent TSS from 2005 to -2019.

SETTING

Referral center.

PATIENTS

CD patients (n = 253) with ACTH measurements before and after TSS.

INTERVENTIONS

TSS for CD.

MAIN OUTCOME MEASURES

Remission after TSS.

RESULTS

Remission was observed in 223 patients after TSS. Those in remission had higher ACTH variability at AM (P = .02) and PM (P < .001) time points compared to nonremission. The nonremission group had a significantly narrower diurnal range compared to the remission group (P = <.0001). A decrease in plasma ACTH of ≥50% from mean preoperative levels predicted CD remission after TSS, especially when using PM values. The absolute plasma ACTH concentration and ratio of preoperative to postoperative values were significantly associated with nonremission after multivariable logistic regression (adj P < .001 and .001, respectively).

CONCLUSIONS

Our findings suggest that ACTH variability is suppressed in CD, and remission from CD is associated with the restoration of this variability. Furthermore, a decrease in plasma ACTH by 50% or more may serve as a predictor of remission post-TSS. These insights could guide clinicians in developing rational outcome measures for interventions targeting CD adenomas.

MECHANISMS IN ENDOCRINOLOGY: A sense of time of the glucocorticoid circadian clock: from the ontogeny to the diagnosis of Cushing's syndrome

The circadian rhythm of glucocorticoids has long been recognised within the last 75 years. Since the beginning, researchers have sought to identify basic mechanisms underlying the origin and emergence of the corticosteroid circadian rhythmicity among mammals. Accordingly, Young, Hall and Rosbash, laureates of the 2017 Nobel Prize in Physiology or Medicine, as well as Takahashi's group among others, have characterised the molecular cogwheels of the circadian system, describing interlocking transcription/translation feedback loops essential for normal circadian rhythms. Plasma glucocorticoid circadian variation depends on the expression of intrinsic clock genes within the anatomic components of the hypothalamic-pituitary-adrenal axis, which are organised in a hierarchical manner. This review presents a general overview of the glucocorticoid circadian clock mechanisms, highlighting the ontogeny of the pituitary-adrenal axis diurnal rhythmicity as well as the involvement of circadian rhythm abnormalities in the physiopathology and diagnosis of Cushing's disease.

Cardiovascular function and glucocorticoid replacement in patients with hypopituitarism

OBJECTIVE

Retrospective analysis suggests an increased mortality from cardiovascular disease in hypopituitary adults; GH deficiency has been postulated to account for this. However, glucocorticoid replacement doses of 30 mg/day of hydrocortisone (HC) may be excessive, and could therefore be implicated in the increased cardiovascular mortality in this group of patients. The aims of this study were to establish whether patients with hypopituitarism have any abnormalities of the cardiovascular system compared to a control group and whether any of these parameters might be improved by reducing the replacement dose of glucocorticoid.

PATIENTS AND MEASUREMENTS

A prospective analysis of cardiovascular function was carried out in 13 patients with hypopituitarism on routine replacement therapy and 20 normal controls who were matched for age and body mass index (BMI). Twenty-four-hour ambulatory blood pressure (BP), erect and supine BP, echocardiography, forearm plethysmography and cardiovascular reflexes in response to tilt, Valsalva and isometric hand grip were performed on controls and on patients taking 30 mg/day of HC and repeated following a reduction in HC dose to 15 mg/day for 3 months. Weight, plasma and urinary electrolytes, 24-hour urinary cortisol excretion, glucose, HbA1C and pituitary function were also assessed on HC 30 mg/day and 15 mg/day.

RESULTS

Mean 24-hour ambulatory BP, in addition to day and night time BP, was lower in patients than in controls (achieving statistical significance in the male subgroup) and did not change significantly with a reduction in HC dose. Erect and supine BP was also lower in patients compared to controls and there was no evidence of postural hypotension following a reduction in HC dose to 15 mg/day. Systolic and diastolic left ventricular dimensions, interventricular septal thickness, ejection fraction and fractional shortening were similar in controls and patients and did not alter with a reduction in HC dose. Systolic and diastolic BP and heart rate responded appropriately to all tests of cardiovascular reflexes (tilt, Valsalva and isometric handgrip) in hypopituitary patients though again measurements of systolic BP were significantly lower in patients during these tests, independent of HC dose. Forearm plethysmography was similar in patients receiving 30 mg of HC and controls but forearm blood flow increased significantly when the HC dose was reduced to 15 mg/day. There was no change in weight, plasma and urinary electrolytes, glucose and HbA1C or pituitary function in the patient group throughout the study.

CONCLUSIONS

In contrast to other studies we have failed to confirm cardiovascular dysfunction in GH deficient hypopituitary adults. Indeed, cardiovascular protection may be conferred on this group by the lower BP levels. Although a reduction in hydrocortisone dose was well tolerated in all patients, it appeared to confer no additional clinical benefit over the 3-month study period. In view of the conflicting data on cardiovascular function in hypopituitary patients, further prospective mortality studies are required in patients with adult GH deficiency.

ACTH precursors characterize the ectopic ACTH syndrome

OBJECTIVE

ACTH is secreted by the pituitary following processing of larger molecular weight precursors, proopiomelanocortin and pro-ACTH. Ectopic ACTH syndrome refers to the secretion of ACTH by non-pituitary tumours, but the predominant circulating form of proopiomelanocortin-related peptides remains unclear.

PATIENTS

Fifteen patients with ectopic ACTH syndrome were compared to 20 patients with pituitary-dependent Cushing's syndrome, 22 patients with small cell lung carcinoma but no evidence of Cushing's syndrome, and 25 controls.

DESIGN AND MEASUREMENTS

Measurement of plasma ACTH and ACTH precursors using specific monoclonal-based immunoradiometric assays at 0900 h and, in five patients with ectopic ACTH syndrome, at 15-minute intervals for 6-24 hours.

RESULTS

ACTH precursors were grossly elevated in patients with ectopic ACTH syndrome (median 2194, range 139-18000 pmol/l) compared to patients with Cushing's disease (median 33, 8-73 pmol/l, P < 0.001), patients with small cell lung carcinomas (38, 8-117 pmol/l, P < 0.001) and controls (26, 10-39 pmol/l, P < 0.001). ACTH levels were also elevated in ectopic ACTH syndrome (0900 h median 34, 11-152 pmol/l) compared to patients with Cushing's disease (0900 h median 8, 3-19 pmol/l), but not to the same degree as ACTH precursors. In contrast with Cushing's disease, ACTH was secreted in a non-pulsatile fashion. ACTH precursors but not ACTH itself correlated with plasma cortisol in patients with ectopic ACTH syndrome (r = 0.65, P < 0.05). Chromatographic analysis of plasma from a patient with ectopic ACTH syndrome confirmed ACTH precursors and not ACTH to be the predominant circulating form. With the cross-reactivity of proopiomelanocortin and pro-ACTH in the ACTH IRMA of < 1 and < 10% respectively, ACTH precursors could represent all the ACTH immunoreactivity in patients with ectopic ACTH syndrome.

CONCLUSIONS

Ectopic 'ACTH' is characterized by aberrant processing of proopiomelanocortin and should be more accurately referred to as 'ectopic ACTH precursor syndrome'.

The hypothalamo-pituitary-adrenal axis across the normal menstrual cycle and in polycystic ovary syndrome

OBJECTIVE

We explored the hypothesis that activation of the hypothalamo-pituitary-adrenal axis is involved in the pathogenesis of hyperandrogenism in the polycystic ovary syndrome.

PATIENTS

Seven women with polycystic ovary syndrome (mean age 27.6 +/- 1.6 (SEM) years) (hirsutism, oligo/amenorrhoea and elevated serum testosterone and dehydroepiandrosterone sulphate) and nine normal female controls (mean age 24.6 +/- 1.5 years) were studied. To exclude anovulation as a confounding factor, four of these normal women were studied in both the follicular and luteal phase of the menstrual cycle.

DESIGN AND MEASUREMENTS

Plasma ACTH and cortisol levels were measured at 15-minute intervals between 0600 h and 1800 h. ACTH and cortisol mean levels, pulse number and amplitude were calculated using established computer software, programmed to identify ACTH and cortisol peaks.

RESULTS

With the exception of mean plasma levels of ACTH over the 12-hour period, which were reduced in the luteal phase of the menstrual cycle (1.8 +/- 0.3 pmol/l) compared to the follicular phase (2.3 +/- 0.2 pmol/l, P < 0.05), there were no differences in the pattern of ACTH or cortisol secretion across the normal cycle. In polycystic ovary syndrome, 12-hour ACTH pulse frequency was reduced (3.6 +/- 0.7) compared with controls (5.9 +/- 0.6, P < 0.05), but cortisol pulsatility and ACTH and cortisol mean levels were similar in both groups.

CONCLUSION

The hyperandrogenism of polycystic ovary syndrome cannot be explained by enhanced ACTH secretion. Normal circulating cortisol levels, yet elevated dehydroepiandrosterone sulphate levels, suggests that polycystic ovary syndrome is yet another example of discrepant adrenal glucocorticoid and androgen secretion, and provides further evidence for a putative adrenal androgen stimulating factor.

A role for life events in the pathogenesis of Cushing's disease

OBJECTIVE

We have previously reported on 30 patients with Cushing's syndrome suggesting an aetiological role for stressful life events. The investigation about life events in the year before the first signs of disease onset was extended to a larger population of patients with Cushing's syndrome, allowing us to differentiate patients with pituitary-dependent and pituitary-independent forms.

DESIGN

Case-control study.

PATIENTS

Sixty-six consecutive patients with Cushing's syndrome of various aetiologies (46 with pituitary-dependent forms and 20 with primary adrenal hyperfunction or ectopic ACTH production) and a control group of 66 healthy subjects, matched for sociodemographic variables, were studied.

MEASUREMENTS

Paykel's Interview for Recent Life Events (a semistructured research interview covering 64 life events) was administered after the acute phase of illness while in remission.

RESULTS

Patients with Cushing's syndrome reported significantly more stressful life events (P < 0.001), both events that had an objective negative impact (P < 0.001) and independent events (P < 0.001), than controls, confirming previous findings. Patients with pituitary-dependent Cushing's disease were compared with their matched controls and reported significantly more total events, events with an objective negative impact and independent events (all at P < 0.001). There were no significant differences between patients with pituitary-independent forms and their matched controls.

CONCLUSIONS

These findings indicate a causal role for stressful life events exclusively in pituitary-dependent Cushing's disease, and suggest a limbic-hypothalamic involvement in the pathogenesis of this condition. The results are similar to those obtained in major depression, and add to other analogies between the two disorders.