Potential risks of glucagon stimulation test in elderly people

The glucagon stimulation test (GST) is a reliable measure for assessing growth hormone (GH) and adrenocorticotropic hormone (ACTH) secretion. The GST is considered to be a safe test, with few mild side effects, especially in adults and in the elderly in whom underlying co-morbidities may be present.

To describe the side effects of the GST in elderly people.

The study was performed with patients of the geriatric ambulatory of our hospital who were recruited to voluntarily participate in a research study concerning the GH and ACTH axis in the elderly people. Forty-two subjects (n=5 males and 37 females) aged 67-88 years, without hypothalamic-pituitary disease, were submitted to the GST. The GST was performed by intramuscular injection of 1mg of glucagon. Blood samples were collected at baseline, and 90, 120, 150, and 180 min after glucagon injection for GH and cortisol measurements.

During the test, 9 subjects (21.4%) had side effects, which included: nausea (14.2%), indisposition (11.9%), hypotension (9.5%), vomiting (7.1%), sweating (4.7%), and dizziness (2.3%). There were four cases of severe symptomatic hypotension, with inaudible blood pressure in two cases. In one case of severe hypotension, the subject suffered two episodes of generalized tonic seizures. Patients who had side effects at GST had statistically higher peak of cortisol (28.9 ± 6.67 μg/dL) and a statistical trend to higher GH peak (8.74 ± 5.96 μg/L). In the group of patients who did not have side effects, the mean cortisol and GH peak were 19.05 ± 5.36 μg/dL and 5.32 ± 3.52 μg/L, respectively.

Although the GST is a reliable alternative test to the ITT, it should be cautiously used in the elderly because this population may have co-morbidities including vascular and cardiac diseases that could be potentiated with side effects of the test, such as severe hypotension.