The GIP/GIPR axis is functionally linked to GH-secretion increase in a significant proportion of gsp- somatotropinomas

OBJECTIVE

Glucose-dependent insulinotropic polypeptide receptor (GIPR) overexpression has been recently described in a proportion of gsp^- somatotropinomas and suggested to be associated with the paradoxical increase of GH (GH-PI) during an oral glucose load.

DESIGN AND METHODS

This study was aimed at linking the GIP/GIPR pathway to GH secretion in 25 somatotropinomas-derived primary cultures and correlating molecular with clinical features in acromegalic patients. Given the impairment of the GIP/GIPR axis in acromegaly, an additional aim was to assess the effect of GH/IGF-1 stimulation on GIP expression in the enteroendocrine cell line STC-1.

RESULTS

Nearly 80% of GIPR-expressing somatotropinomas, all of them negative for gsp mutations, show increased GH secretion upon GIP stimulation, higher sensitivity to Forskolin but not to somatostatin analogs. Besides increased frequency of GH-PI, GIPR overexpression does not appear to affect acromegalic patients' clinical features. In STC-1 cells transfected with GIP promoter-driven luciferase vector, IGF-1 but not GH induced dose-dependent increase in luciferase activity.

CONCLUSIONS

We demonstrate that GIPR mediates the GH-PI in a significant proportion of gsp^- acromegalic patients. In these cases, the stimulatory effect of IGF-1 on GIP promoter support the hypothesis of a functional GH/IGF-1/GIP axis. Further studies based on larger cohorts and the development of a stable transgenic model with inducible GIPR overexpression targeted to pituitary somatotroph lineage will be mandatory to establish the real role of GIPR in the pathogenesis of somatotropinomas.

A multicenter experience on the prevalence of ARMC5 mutations in patients with primary bilateral macronodular adrenal hyperplasia: from genetic characterization to clinical phenotype

ARMC5 mutations have recently been identified as a common genetic cause of primary bilateral macronodular adrenal hyperplasia (PBMAH). We aimed to assess the prevalence of ARMC5 germline mutations and correlate genotype with phenotype in a large cohort of PBMAH patients. A multicenter study was performed, collecting patients from different endocrinology units in Italy. Seventy-one PBMAH patients were screened for small mutations and large rearrangements in the ARMC5 gene: 53 were cortisol-secreting (two with a family history of adrenal hyperplasia) and 18 were non-secreting cases of PBMAH. Non-mutated and mutated patients' clinical phenotypes were compared and related to the type of mutation. A likely causative germline ARMC5 mutation was only identified in cortisol-secreting PBMAH patients (one with a family history of adrenal hyperplasia and ten apparently sporadic cases). Screening in eight first-degree relatives of three index cases revealed four carriers of an ARMC5 mutation. Evidence of a second hit at somatic level was identified in five nodules. Mutated patients had higher cortisol levels (p = 0.062), and more severe hypertension and diabetes (p < 0.05). Adrenal glands were significantly larger, with a multinodular phenotype, in the mutant group (p < 0.01). No correlation emerged between type of mutation and clinical parameters. ARMC5 mutations are frequent in cortisol-secreting PBMAH and seem to be associated with a particular pattern of the adrenal masses. Their identification may have implications for the clinical care of PBMAH cases and their relatives.

An analysis of different therapeutic options in patients with Cushing's syndrome due to bilateral macronodular adrenal hyperplasia: a single-centre experience

CONTEXT

Bilateral macronodular adrenal hyperplasia (BMAH) is a rare form of Cushing's syndrome (CS). A variety of in vivo tests to identify aberrant receptor expression have been proposed to guide medical treatment. Unilateral adrenalectomy (UA) may be effective in selected patients, but little is known about recurrence during follow-up.

OBJECTIVE

To describe a series of patients with BMAH and CS treated by different approaches, with a particular focus on the benefit of UA.

DESIGN AND PATIENTS

We retrospectively assessed 16 patients with BMAH and CS (11 females, five males), analysing the in vivo cortisol response to different provocative tests. Twelve of the 16 patients underwent UA and were monitored over the long term.

RESULTS

Based on in vivo test results, octreotide LAR or propranolol was administered in one case of food-dependent CS and two patients with a positive postural test. A significant improvement in biochemical values was seen in all patients but with limited clinical response. UA was performed in 12 patients, producing long-term remission in three (106 ± 28 months; range: 80-135), recurrence in eight (after 54 ± 56 months; range 12-180) and persistence in one other. Four patients subsequently underwent contralateral adrenalectomy for overt CS, one received ketoconazole, and four other patients remain under observation for subclinical CS.

CONCLUSIONS

Medical treatment based on cortisol response to provocative tests had a limited role in our patients, whereas UA was useful in some of them. Although recurrence is likely, the timing of onset is variable and close follow-up is mandatory to identify it.

Venous thromboembolism in patients with Cushing's syndrome: need of a careful investigation of the prothrombotic risk profile

A high incidence of venous thromboembolic (VTE) complications has been reported in Cushing's syndrome (CS), mostly post-operatively and attributable to hypercoagulability. The prevalence of symptomatic VTE was investigated retrospectively in 58 consecutive CS patients in relation to acquired and genetic thrombotic risk factors. Eight CS patients (14 %) developed VTE (group A), 3 of them related and 5 unrelated to surgery. These patients had higher urinary free cortisol (p = 0.01) and VWF levels (p = 0.02) than the 50 patients without VTE (group B), as well an increase in the hemostatically more efficient, high-molecular-weight VWF multimers (p = 0.002). Factor V Leiden and the prothrombin gene 20210A variants (the most common inherited thrombophilic defects) were more represented in group A than in group B, as was the genotype GCAG/GCAG of the VWF gene promoter, known to hyperinduce VWF upregulation under cortisol excess. All but one of the patients with VTE unrelated to surgery had at least four acquired and at least one inherited risk factor. Severe hypercortisolism and VWF levels with increased haemostatic activity are strongly associated with VTE in CS. VTE episodes unrelated to surgery are attributable to the synergistic action of acquired and inherited thrombotic risk factors. Based on these observations, we believe that severely affected CS patients should be screened for coagulation disorders and receive antithrombotic prophylaxis whenever they have concomitant prothrombotic risk factors.

Adrenal nodules in patients with Cushing's disease: prevalence, clinical significance and follow-up

Adrenal glands in Cushing's disease (CD) range from normal to showing diffuse enlargement in most cases. The finding of nodular lesions has been reported, but information about prevalence and evolution is described in few reports.

AIM

To investigate the prevalence of nodular adrenal glands in patients with CD and assess its evolution after disease remission.

SUBJECTS AND METHODS

We assessed 41 CD patients' abdominal computed tomography (CT) scans obtained during the active phase of the disease and evaluated the dynamics of ACTH and cortisol secretion. CT was repeated after disease remission in patients with adrenal nodules.

RESULTS

Fifteen of 41 patients had nodular and the remaining 26 had normal or enlarged adrenal glands. Patients with nodules were older (45.1 ± 8.8 vs 36.9 ± 12.7 yr; p=0.03) and had longer-standing disease (57.3 ± 56.9 vs 32.9 ± 29.1 months; p=0.05) than patients with normal/enlarged adrenal glands. ACTH (45.4 ± 21.3 vs 70.5 ± 39.1 pg/ml; p=0.04) and urinary free cortisol levels (606.1 ± 512.3 vs 301.0 ± 224.7 μg/day, p=0.01) were significantly lower in patients with adrenal nodules while there were no differences between the groups in terms of dynamic tests results. Post-operative follow-up showed regression or shrinkage of the nodules in 8 out of 10 patients in disease remission.

CONCLUSIONS

We found that adrenal nodular glands are a frequent finding in CD in particular in older patients and in those with a longerstanding disease. Nevertheless, a high percentage of nodules regression or shrinking was evidenced in our series after disease remission.

Adrenal lesions in acromegaly: do metabolic aspects and aryl hydrocarbon receptor interacting protein gene have a role? Evaluation at baseline and after long-term follow-up

BACKGROUND

Adrenal lesions are discovered in acromegaly more frequently than in general population, without relationship with primary disease. Some patients, carriers of aryl hydrocarbon receptor interacting protein (AIP) gene mutations, developed an adrenal neoplasm.

AIM

To evaluate the role of metabolic and genetic aspects and the follow-up of adrenal nodules in acromegaly.

MATERIAL AND METHODS

We studied 69 acromegalic patients (30 male and 39 female, 56 ± 15 yr) who had been referred to the Endocrinology Unit of Padua. In all patients we determined body mass index (BMI) and waist-to-hip ratio (WHR); we performed an oral glucose tolerance test (OGTT) whenever possible. If adrenal computed tomography revealed a lesion, the patient underwent an endocrine and genetic study.

RESULTS

Adrenal lesions were identified in 14 patients and were not related to gender, duration of disease, GH or IGF-I concentrations, basal and after-OGTT glucose and insulin levels, log(HOMA-IR) and Quantitative Insulin Sensitivity Check Index (QUICKI) values, whereas BMI and WHR were higher in patients with adrenal lesions. Baseline endocrine and radiological study revealed benign lesions; during mean 4-yr follow-up none of the patients showed hormone excess, even though some lesions increased in size. We did not find any mutation in AIP gene, except heterozygous silent alteration (T48T).

CONCLUSIONS

The frequency of non-functioning adrenal lesions in acromegaly is not associated with the considered aspects, except BMI and WHR. The prolonged follow-up showed that these lesions have a tendency to increase in size independently of the control of acromegaly, so a morphological follow- up is recommended.

A case of primary aldosteronism in pregnancy: do LH and GNRH receptors have a potential role in regulating aldosterone secretion?

OBJECTIVE

The mechanisms inducing steroidogenesis in primary aldosteronism (PA) remain poorly defined. It was recently demonstrated that some G-protein-coupled receptors are abnormally expressed in aldosterone-producing adenomas (APA). We evaluated the potential role of LH and GNRH receptors (LHR (or LHCGR) and GNRHR) in regulating aldosterone secretion in a patient with APA arising during pregnancy (index case) and in a subset of other patients with PA.

PATIENTS AND METHODS

GNRH test was performed in the index case, 11 other PA, and 5 controls. GNRHR and LHR expressions were examined in 23 APA and 6 normal tissues.

RESULTS

Aldosterone response increased significantly (114%) in the index case after GNRH test was performed preoperatively, while it was blunted after adrenalectomy. Aldosterone also increased after human chorionic gonadotropin and triptorelin stimulation. A partial aldosterone response to GNRH was observed in other 7/11 PA, while a significant response was observed in two patients. Controls did not respond to GNRH test. GNRHR was overexpressed and LHR expression was moderate in the APA tissue from the index case. Moreover, LHR was found in normal adrenals and overexpressed in 6/22 APA. GNRHR was overexpressed in 6/22 APA, 2 of them with a 95- and 109-fold higher expression than normal. A correlation between the clinical and molecular findings was observed in five out of seven patients.

CONCLUSION

We describe a case of PA diagnosed during pregnancy, which appeared to correlate with aberrant LHR and GNRHR expression. Our findings suggest that a subset of patients with PA has aberrant LHR and GNRHR expression, which could modulate aldosterone secretion.

Food-dependent Cushing's syndrome: from molecular characterization to therapeutical results

OBJECTIVE

Cortisol secretion in ACTH-independent macronodular adrenal hyperplasia (AIMAH) may be regulated by the aberrant expression of several G-protein-coupled receptors. Bilateral adrenalectomy is the treatment of choice in most cases. We searched for aberrant receptor expression in a patient with AIMAH and evaluated the response to medical and surgical treatment.

PATIENT

A 35-year-old woman with amenorrhea, hirsutism, and hypertension presented ACTH-independent cortisol secretion with high androgen levels. Abdominal computed tomography showed bilateral adrenal macronodules (4.5 cm right and 1.0 cm left). Scintigraphy with I(131)-norcholesterol showed bilateral uptake, prevalent on the right side. Several in vivo stimulation tests were assessed before and after treatment and in vitro studies were performed after unilateral adrenalectomy.

RESULTS

Plasma cortisol increased after a standard meal test (60%) and oral glucose loading (147%), and the response was blunted by pretreatment with 100 microg s.c. octreotide. The therapy with long-acting release octreotide (octreotide-LAR) showed an improvement in urinary free cortisol (UFC) levels. Unilateral adrenalectomy was performed and histopathology revealed macronodular AIMAH. Cortisol and androgens increased after perifusion of tumoral tissue with glucose-dependent insulinotropic polypeptide (GIP), and GIP and LH-receptor overexpression was found in both the adrenal nodules and the adjacent cortex. After surgery, UFC and androgen levels normalized followed by clinical improvement.

CONCLUSIONS

GIP and LH-receptor expression may coexist in AIMAH, influencing the functional and morphological phenotype. Aberrant hormone receptor expression enables specific pharmacological treatment, but long-term studies are needed to evaluate its real efficacy. Unilateral adrenalectomy may be a safe initial option, particularly for asymmetric bilateral adrenal enlargements.