Investigation of the clinical significance of the growth hormone-releasing peptide-2 test for the diagnosis of secondary adrenal failure

Clinical investigation of a unique type of hypothalamic adrenal insufficiency

Hypothalamic adrenal insufficiency (AI) is a rare but distinct type of AI. The leading cause of hypothalamic AI is a secondary side-effect of exogenous steroid intake, particularly in large amounts and/or long-term periods. The next cause would be the effect of the tumor in the hypothalamic lesions. We show here 9 cases of hypothalamic AI without any disorder on imagings and a history of steroid administration. All patients had general fatigue; 7 patients (77.8%) had a history of hypoglycemia; 5 patients (55.6%) had a history of hypotension. None of the patients had hyponatremia, hyperkalemia, or eosinophilia. Their morning plasma adrenocorticotropic hormone (ACTH) value was low at 8.5 ± 4.2 pg/mL, and serum cortisol value was low at 4.5 ± 1.3 µg/dL. All patients demonstrated normal responses during the corticotropin-releasing hormone loading (CRH) test but inadequate responses during the insulin tolerance test (ITT). After hydrocortisone replacement therapy, their morning plasma ACTH and serum cortisol values were significantly recovered (P < .05). Moreover, more than half of the patients were fine after discontinuing hydrocortisone replacement therapy. These results indicate that this unique type of hypothalamic AI has a curable clinical course making hydrocortisone replacement therapy a novel therapeutic option.

Clinical usefulness of the growth hormone-releasing peptide-2 test for hypothalamic-pituitary disorder

Purpose

Growth hormone deficiency (GHD) develops early in patients with hypothalamic-pituitary disorder and is frequently accompanied by other anterior pituitary hormone deficiencies including secondary adrenal insufficiency (AI). A growth hormone-releasing peptide-2 (GHRP2), which is wildly used for the diagnosis of patients with GHD, has been considered to induce not only growth hormone (GH) release but also ACTH release. However, its clinical usefulness in hypothalamic-pituitary disorder is unclear.

Methods

The GHRP2 test, a cosyntropin stimulation test, corticotropin-releasing hormone (CRH) tests and/or insulin tolerance tests (ITTs) were performed on 36 patients having hypothalamic-pituitary disorder.

Results

Twenty-two (61%) had severe GHD, and 3 (8%) had moderate GHD by GHRP2. There was no difference in baseline ACTH and cortisol between non-GHD, moderate GHD and severe GHD participants. However, a cosyntropin stimulation test and subsequent CRH tests and/or ITTs revealed that 17 (47%) had secondary AI and 16/17 (94%) cases of secondary AI were concomitant with severe GHD. ROC curve analysis demonstrated that the ACTH response in the GHRP2 test was useful for screening pituitary-AI, with a cut-off value of 1.55-fold (83% sensitivity and 88% specificity). Notably, the combination of ACTH response and the peak cortisol level in the GHRP2 test using each cut-off value (1.55-fold and 10 µg/dl, respectively) showed high specificity (100%) with high accuracy (0.94) for diagnosis of pituitary-AI.

Conclusion

We recommend measuring ACTH as well as GH during the GHRP2 test to avoid overlooking and delays in diagnosis of secondary AI that frequently accompanies GHD.

Secondary Adrenal Insufficiency: Recent Updates and New Directions for Diagnosis and Management

Secondary adrenal insufficiency is the most common subtype of adrenal insufficiency; it is caused by certain medications and pituitary destruction (pituitary masses, inflammation, or infiltration) and is rarely associated with certain germline variants. In this review, we discuss the etiology, epidemiology, and clinical presentation of secondary adrenal insufficiency and focus on the diagnostic and management challenges. We also review the management of selected special populations of patients and discuss patient-important outcomes associated with secondary adrenal insufficiency.

Investigation of the Hypothalamo-pituitary-adrenal (HPA) axis: a contemporary synthesis

The hypothalamo-pituitary-adrenal (HPA) axis is one of the main components of the stress system. Maintenance of normal physiological events, which include stress responses to internal or external stimuli in the body, depends on appropriate HPA axis function. In the case of severe cortisol deficiency, especially when there is a triggering factor, the patient may develop a life-threatening adrenal crisis which may result in death unless early diagnosis and adequate treatment are carried out. The maintenance of normal physiology and survival depend upon a sufficient level of cortisol in the circulation. Life-long glucocorticoid replacement therapy, in most cases meeting but not exceeding the need of the patient, is essential for normal life expectancy and maintenance of the quality of life. To enable this, the initial step should be the correct diagnosis of adrenal insufficiency (AI) which requires careful evaluation of the HPA axis, a highly dynamic endocrine system. The diagnosis of AI in patients with frank manifestations is not challenging. These patients do not need dynamic tests, and basal cortisol is usually enough to give a correct diagnosis. However, most cases of secondary adrenal insufficiency (SAI) take place in a gray zone when clinical manifestations are mild. In this situation, more complicated methods that can simulate the response of the HPA axis to a major stress are required. Numerous studies in the assessment of HPA axis have been published in the world literature. In this review, the tests used in the diagnosis of secondary AI or in the investigation of suspected HPA axis insufficiency are discussed in detail, and in the light of this, various recommendations are made.

Reversible Non-parkinsonian Bradykinesia with Impaired Frontal Lobe Function as the Predominant Manifestation of Adrenal Insufficiency

A 69-year-old Japanese man with a history of suprasellar surgery and irradiation developed bradykinesia and mild fatigue without muscle weakness, myalgia, pyramidal or extrapyramidal signs, parkinsonian symptoms, or ataxia. An endocrinological work-up revealed anterior hypopituitarism associated with secondary adrenal insufficiency. Higher brain function tests indicated an impaired frontal lobe function. The patient's bradykinesia, fatigue, and frontal lobe dysfunction improved within 2 weeks after the initiation of corticosteroid replacement therapy. To our knowledge, this is the first reported case of adrenal insufficiency manifesting as non-parkinsonian bradykinesia. Physicians should consider reversible non-parkinsonian bradykinesia associated with frontal lobe dysfunction as an unusual manifestation of adrenal insufficiency.

Evaluation of Hypothalamic-Pituitary-Adrenal Axis by the GHRP2 Test: Comparison With the Insulin Tolerance Test

Context

GH-releasing peptide 2 (GHRP2) stimulates the hypothalamic–pituitary–adrenal axis (HPA) through the GH secretagogue receptor (GHSR) in the hypothalamus, in which ghrelin is a natural ligand. Therefore, the GHRP2 test (GHRP2T) could be used instead of the insulin tolerance test (ITT).

Objective

Can the GHRP2T replace the ITT for evaluation of HPA?

Design

The present retrospective study analyzed the clinical features and laboratory data from 254 patients admitted for evaluation of hypopituitarism who underwent both GHRP2T and ITT. We analyzed the association between the maximum cortisol level (Fmax) during both tests. Adrenocortical insufficiency was diagnosed by ITT. The suitability of GHRP2T was examined using the receiver operating characteristic curve.

Results

A strong correlation was found between Fmax measured using both tests (r = 0.777, P < 0.0001). However, the sensitivity (64%) and specificity (79%) showed that the GHRP2T was not suitable for clinical use. Various factors influenced the correlation, probably through their effects on ghrelin and/or GHSR, including functional adenoma (P < 0.05) and sex (P < 0.05). No substantial correlation was found between Fmax measured using both tests in patients with prolactinoma (n = 30). The exclusion of patients with functional adenoma revealed no factors that affected the association in male patients; however, age and menstruation significantly influenced it in female patients (P < 0.05). Analysis of the data from male subjects without functional adenoma (n = 104) showed high sensitivity (95%) and specificity (85%) for the GHRP2T.

Conclusion

ITT can be substituted with GHRP2T for assessment of HPA in male patients free of functional adenoma.