Evaluation of GH reserve in patients with adrenal incidentalomas and biochemical evidence of subclinical autonomous glucocorticoid hypersecretion

MECHANISMS IN ENDOCRINOLOGY: Endogenous subclinical hypercortisolism and bone: a clinical review

In recent years, the condition of subclinical hypercortisolism (SH) has become a topic of growing interest. This is due to the fact that SH prevalence is not negligible (0.8-2% in the general population) and that, although asymptomatic, this subtle cortisol excess is not harmless, being associated with an increased risk of complications, in particular of osteoporosis and fragility fractures. As specific symptoms of hypercortisolism are absent in SH, the SH diagnosis relies only on biochemical tests and it is a challenge for physicians. As a consequence, even the indications for the evaluation of bone involvement in SH patients are debatable and guidelines are not available. Finally, the relative importance of bone density, bone quality and glucocorticoid sensitivity in SH is a recent field of research. On the other hand, SH prevalence seems to be increased in osteoporotic patients, in whom a vertebral fracture may be the presenting symptom of an otherwise asymptomatic cortisol excess. Therefore, the issue of who and how to screen for SH among the osteoporotic patients is widely debated. The present review will summarize the available data regarding the bone turnover, bone mineral density, bone quality and risk of fracture in patients with endogenous SH. In addition, the role of the individual glucocorticoid sensitivity in SH-related bone damage and the problem of diagnosing and managing the bone consequences of SH will be reviewed. Finally, the issue of suspecting and screening for SH patients with apparent primary osteoporosis will be addressed.

GH secretion reserve in subclinical hypercortisolism

PURPOSE

In overt hypercortisolism, growth hormone (GH) secretion is decreased and normalizes after surgery. In subclinical hypercortisolism (SH), GH secretion has been scarcely investigated. We assessed GH reserve in patients with and without SH and, in the former, also after recovery.

METHODS

We enrolled 24 patients with adrenal adenomas, 12 with SH (SH+, 8 females, 58.3 ± 6.5 years) and 12 without SH (SH-; 11 females, 61.8 ± 10.6 years). SH was diagnosed in the presence of ≥ 2 out of: 1 mg overnight dexamethasone suppression test >83 nmol/L, urinary free cortisol (UFC) >193 nmol/day and ACTH levels <2.2 pmol/L. GH secretion was assessed by GHRH + Arginine test (GHRH-ARG) and age-adjusted serum IGF-I levels, expressed as SDS (IGF-I SDS). Eight SH+ patients were re-evaluated after the recovery from SH.

RESULTS

Age, gender, body mass index (BMI) and IGF-I SDS were comparable between SH+ and SH- patients. After GHRH-ARG the mean GH peak levels (GH-P) and GH response (as Area Under Curve, GH-AUC) were lower in SH+ than in SH- patients (15.2 ± 8.1 vs 44.5 ± 30.9 μg/L, P = 0.004 and 1,418 ± 803 vs 4,028 ± 2,476 μg/L/120 min, P = 0.002, respectively), after adjusting for age and BMI. The GH-AUC and GH-P levels were negatively associated with UFC after adjusting for age and BMI (β = -0.39, P = 0.02 and β = -0.4, P = 0.020 respectively). After recovery, GH-P levels and GH-AUC increased as compared to baseline (23.7 ± 16.3 vs 15.8 ± 10.2 μg/L, P = 0.036 and 2,549 ± 1,982 vs 1,618 ± 911 μg/L/120 min, P = 0.012, respectively).

CONCLUSIONS

GH secretion reserve is decreased in SH patients and increases after the recovery.

Endogenous subclinical hypercortisolism: Diagnostic uncertainties and clinical implications

Subclinical hypercortisolism (SH) is a newly characterized hormonal disorder that is almost exclusively detected in the context of incidentally discovered adrenal masses. The diagnostic criteria used for the definition of this condition are at present controversial. Amongst the various tests used for the detection of this abnormality (dexamethasone suppression, urinary free cortisol, ACTH levels, midnight serum or salivary cortisol concentrations, ACTH responses to CRH stimulation), the dexamethasone suppression tests (DST) seem to better accomplish the task of unmasking subtle abnormalities of cortisol secretion. Several versions of DST have been used: the 1-mg overnight, the 3-mg overnight and the classical 2-day low-dose DST. This latter test has the theoretical advantage that, by more efficiently suppressing pituitary ACTH secretion, it may provide a measure of the residual (ie non- ACTH-dependent) cortisol secretion from the adrenal mass. In this way, post-dexamethasone cortisol concentrations may quantify the degree of autonomous cortisol hypersecretion. In fact, post-dexamethasone cortisol concentrations have a negative correlation with basal ACTH levels and a positive correlation with midnight cortisol concentrations as well as the size of the incidentally discovered adrenal mass. Most of the existing data indicate that SH detected in the context of adrenal incidentalomas may have some clinically significant implications. In fact, patients with higher post-dexamethasone cortisol concentrations demonstrate higher lipid levels and lower bone mass densities. It has also been suggested that SH may be responsible for biochemical and phenotypic changes reminiscent of the metabolic syndrome. In summary, SH does exist and is associated with a negative impact in patients' health; however, hormonal cut-off criteria for decision-making remain to be defined.