Glucagon stimulation test: has its time come?

Regulation of the Cortisol Axis, Glucagon, and Growth Hormone by Glucose Is Altered in Prediabetes and Type 2 Diabetes

CONTEXT

Insulin-antagonistic, counter-regulatory hormones have been implicated in the development of type 2 diabetes (T2D).

OBJECTIVE

In this cross-sectional study, we investigated whether glucose-dependent regulation of such hormones differ in individuals with T2D, prediabetes (PD), and normoglycemia (NG).

METHODS

Fifty-four individuals with or without T2D underwent one hyperinsulinemic-normoglycemic-hypoglycemic and one hyperglycemic clamp with repeated hormonal measurements. Participants with T2D (n = 19) were compared with a group-matched (age, sex, BMI) subset of participants without diabetes (ND, n = 17), and also with participants with PD (n = 18) and NG (n = 17).

RESULTS

In T2D vs ND, glucagon levels were higher and less suppressed during the hyperglycemic clamp whereas growth hormone (GH) levels were lower during hypoglycemia (P < .05). Augmented ACTH response to hypoglycemia was present in PD vs NG (P < .05), with no further elevation in T2D. In contrast, glucagon and GH alterations were more marked in T2D vs PD (P < .05).In the full cohort (n = 54), augmented responses of glucagon, cortisol, and ACTH and attenuated responses of GH correlated with adiposity, dysglycemia, and insulin resistance. In multilinear regressions, insulin resistance was the strongest predictor of elevated hypoglycemic responses of glucagon, cortisol, and ACTH. Conversely, fasting glucose and HbA1c were the strongest predictors of low GH levels during hypoglycemia and elevated, i.e. less suppressed glucagon levels during hyperglycemia, respectively. Notably, adiposity measures were also strongly associated with the responses above.

CONCLUSIONS

Altered counter-regulatory hormonal responses to glucose variations are observed at different stages of T2D development and may contribute to its progression by promoting insulin resistance and dysglycemia.

Management of hypopituitarism: a perspective from the Brazilian Society of Endocrinology and Metabolism

Hypopituitarism is a disorder characterized by insufficient secretion of one or more pituitary hormones. New etiologies of hypopituitarism have been recently described, including head trauma, cerebral hemorrhage, and drug-induced hypophysitis. The investigation of patients with these new disorders, in addition to advances in diagnosis and treatment of hypopituitarism, has increased the prevalence of this condition. Pituitary hormone deficiencies can induce significant clinical changes with consequent increased morbidity and mortality rates, while hormone replacement based on current guidelines protects these patients. In this review, we will first discuss the different etiologies of hypopituitarism and then address one by one the clinical aspects, diagnostic evaluation, and therapeutic options for deficiencies of TSH, ACTH, gonadotropin, and GH. Finally, we will detail the hormonal interactions that occur during replacement of pituitary hormones.

[Comparative study of glucagon and insulin tests for diagnostics of secondary adrenal insufficiency and growth hormone deficiency in children and adolescents]

BACKGROUND

Diagnostics of growth hormone deficiency (GHD) and secondary adrenal insufficiency (SAI) is based on estimation of peak GH and cortisol concentrations in provocation tests. Russian consensus on diagnostics and treatment of hypopituitarism in children and adolescences recommends to measure GH and cortisol concentrations in every time-point of insulin test (IT). Glucagon test (GT) is discussed in literature as alternative to IT.

AIMS

To estimate the possibility to use provocation GT for diagnostics of SAI and GHD in children and adolescents.

MATERIALS AND METHODS

We investigated blood and urine cortisol levels, IT, and GT in 20 patients 6.5-17.8 years (Me 13.0 (10.4; 15.3)) after surgery and/or radiology and/or chemical therapy of head and neck tumors; remission for 0.4-7.5 years (Ме 2.1 (1.5; 5.2)).

RESULTS

With cut-off point 550 nmol/L sensitivity and specifity of IT was 100% and 60%, GT - 100% and 53% respectively. Minimal cortisol cut-off level for GT with sensitivity 100% was 500 nmol/L, maximal with specifity 100% - 400 nmol/L.Early morning cortisol levels did not exceed 250 nmol/l in 2 patients with SAI; and were above 500 nmol/l in 8 patients without SAI while primary or repeated examination.GHD was reviled by IT in all patients. Maximal GH concentrations in GT and IT did not differ significantly (p&gt;0.05) but GT results of 4 patients exceeded or met cut-off for this test (7 ng/ml).GT was characterized by less severity compared with IT.

CONCLUSIONS

For diagnostics of SAI by GT we can advise cut-off points of cortisol level 500 (sensitivity 100%, specifty 53%) and 400 nmol/L (sensitivity 80%, specifity 100%). Measuring of cortisol levels in 2-3 early morning blood samples allows to exclude or to suspect SAI in half of patients before tests. GH peaks in GT can exceed similarly data in IT that needs future investigation.

[Current aspects of diagnosis and treatment of adult GH-deficiency]

Adult growth hormone (GH) deficiency (AGHD) is a condition characterized by alterations in body composition, lipid and carbohydrate metabolism, bone mineral density and poor quality of life; however, clinical presentations of AGHD are mostly non-specific. Untreated AGHD is associated with increased cardiovascular morbidity and mortality. Stimulation tests are used for the diagnosis: insulin tolerance test, glucagon stimulation test, growth-hormone releasing hormone and arginine stimulation test. Moreover, in 2017 FDA approved the use of macimorelin (oral GH secretagogue) for the diagnosis of AGHD. In childhood GH-deficiency, apolipoprotein A-IV, CFHR4 (complement factor H-related protein 4) and PBP (platelet basic protein) were identified as potential biomarkers of the disease, however, this was not investigated in AGHD. GH treatment starts from the minimal dose, which allows minimizing the adverse effects. According to published meta-analyses, AGHD treatment generally does not lead to increased risk of malignancy and recurrence of sellar neoplasms in adult patients. Published data on GH receptor polymorphism associations with treatment efficacy remains controversial. Development of long-acting GH formulations is a currect perspective for the increase of treatment compliance.

Update on GH therapy in adults

Over the last three decades, short- and long-term observational studies, clinical trials, systematic reviews, and meta-analyses have provided relevant information on the efficacy and safety of growth hormone (GH) replacement therapy in adults with GH deficiency (AGHD). The knowledge acquired during this time has been compiled into different guidelines that offer clinicians an evidence-based, practical approach for the management of AGHD. There are, however, still open questions in some key areas in which recommendations are supported by only moderate or weak evidence. In the last recent years, the development of long-acting GH preparations has created new therapeutic possibilities by decreasing injection frequency, improving adherence and thereby potentially maximizing clinical outcomes. The aims of this review are to advance our understanding on the diagnosis and treatment of AGHD and to present an update and future perspectives on the use of long-acting GH preparations.