Diazepam Test of Growth Hormone Secretion

Summary

Diazepam induced growth hormone (GH) secretion was studied in six healthy subjects, twenty hypopituitary and five acromegalic patients. Plasma GH, blood glucose and diazepam levels were determined. Diazepam (0.2 mg/kg b.w.) consistently induced GH secretion in control and acromegalic subjects. Oral diazepam produced a peak level (21.2 ± 3.2 ng/ml) at 40 minutes in six control subjects and GH returned to basal levels at 90 minutes (3.8 ± 1.2 ng/ml). In twenty hypopituitary subjects with basal GH level of 1.7 ± 0.5 ng/ml, the peak GH after oral diazepam (4.3 ± 1.2 ng/ml) was significantly blunted (p < 0.001). In four acromegalic patients, the elevated basal GH level (29.6 ± 9.0 ng/ml) increased further to a peak at 40 minutes (92.7 ± 15.1 ng/ml) and remained high up to 90 minutes (p < 0.001). No GH response was obtained in three hypopituitary and one acromegalic patients.

The peak GH level at 20 minutes after intramuscular injection of diazepam (10 mg) was 14.3 ± 3.7 ng/ml in control, 3.0 ± 0.4 ng/ml in five hypopituitary and 54.4 ± 13.1 ng/ml in acromegalic subjects. No significant change in blood glucose was seen after diazepam stimulation. A comparison was made between the GH responses to diazepam and insulin induced hypoglycemia in hypopituitarism and acromegaly. Both tests caused adequate release of GH from the pituitary gland in five control subjects who had normal GH reserve. The peak GH responses of the two tests were similar in magnitude in control subjects and were correlated (r = 0.77; p < 0.001). In five hypopituitary subjects both the tests failed to evoke a satisfactory GH response thus confirming the deficiency of GH. In four acromegaly subjects, diazepam raised serum GH to a higher level than insulin induced hypoglycemia. Diazepam stimulation does not require prior preparation of the patient and is relatively free of side effects. Consequently, we suggest that diazepam induced GH secretion is a simple, reliable test of pituitary function useful in the assessment of hypopituitarism and acromegaly.

Key-Words:

Growth Hormone - Diazepam - Hypopituitarism - Acromegaly