Evaluation of the pituitary function with insulin tolerance (hypoglycaemia) testing: are there any differences using insulin lispro compared to regular insulin?

BACKGROUND/AIM: The insulin tolerance test (ITT) remains the gold standard for evaluating the pituitary function, but has potential risks when hypoglycaemia is induced. There are scarce data using short-acting insulin analogs for ITTs. This pilot study compares the effects of insulin lispro (LPI) with regular insulin (RGI) during an ITT.

METHODS

Patients with suspected hypopituitarism (n = 103) randomly received either LPI (n = 51) or RGI (n = 52).

RESULTS

All patients reported signs and symptoms when hypoglycaemia was induced. In the LPI group, hypoglycaemia occurred sooner (23.6 +/- 1.6 vs. 28.3 +/- 1.4 min, p < 0.05), and duration of hypoglycaemia (25.0 +/- 1.7 vs. 31.9 +/- 1.9 min, p < 0.05) and time for blood glucose levels to return to a 'safe' level (>3.3 mmol/l; 56.5 +/- 2.3 vs. 76.0 +/- 2.1 min, p < 0.001) were shorter as compared with the RGI group. No differences in peak growth hormone and cortisol levels were observed between the two groups.

CONCLUSIONS

Our data suggest that despite inducing similar symptomatology, LPI exerted a quicker onset and a shorter duration of hypoglycaemia as compared with RGI. Thus, using LPI might reduce the potential risks associated with an ITT by shortening the hypoglycaemic phase of the test.