Adrenocortical, somatotropic, and antidiuretic response to nasal glucagon in healthy subjects

Objective: The glucagon stimulation test involves the peptide intramuscular or subcutaneous administration for the diagnosis of hypopituitarism. To date, no data are available regarding its intranasal formulation. Our study intended to investigate the role of intranasal glucagon as a potential stimulus test for the evaluation of the corticotropic, somatotropic, and antidiuretic axes.

Design: Non-randomized, single-blinded, cross-over study including 10 healthy subjects (50% women).

Methods: All participants underwent 2 days of testing, and intranasal glucagon or placebo was administered. At baseline, every 15' up to +90', and then every 30' up to +180', a blood sample was taken for adrenocorticotropic hormone (ACTH), cortisol, growth hormone (GH), copeptin, glucose, insulin, sodium, potassium, and plasma osmolarity. At baseline and at the end of the test, urinary osmolarity was evaluated as well.

Results: After administration of both glucagon and placebo, ACTH and cortisol values decreased progressively (P < 0.001), but in the drug group, the reduction in cortisol was less accentuated up to +90' (P < 0.05). Growth hormone values decreased after placebo administration (P < 0.001); on the other hand, after glucagon, an increasing, yet non-significant trend was observed (P = 0.096) with the difference between the two groups evident starting from +120' onwards (P < 0.005). The placebo administration led to a reduction of copeptin, while its stability was observed after glucagon administration. Six subjects developed hypokalemia (ie, potassium <3.5 mmol/L) post-glucagon, with the nadir at 45' (3.6 [3.2-3.8] mmol/L) significantly correlated with the immediate post-glycemic rise insulin peak (Spearman's rho -0.719; P = 0.019). No significant differences were observed compared to the other analytes tested.

Conclusions: Intranasal glucagon administration is not an effective stimulus for hypophyseal secretion. Hypokalemia secondary to hyperinsulinemic rebound appears to be a frequent complication of its acute administration.