Pituitary-independent effects of octreotide

Somatostatin analogues are used to suppress pituitary GH secretion in acromegaly patients. This study by Pokrajac et al. studied octreotide, the first synthetic somatostatin analogue proven to suppress pituitary GH, for its pituitary-independent effects. The aim was to study the hypothesis that octreotide lowers serum IGF1 by inhibiting GH stimulation of IGF1 synthesis, in addition to inhibiting GH secretion.

The study used 11 severely GH-deficient patients who had been receiving a stable dose of GH replacement for at least 6 months. Patients received 50 μg of subcutaneous octreotide three times a day for seven days and blood samples were taken and assayed. The study found that octreotide resulted in a decrease in total IGF1, free IGF1, and IGFBP3. Octreotide also induced a decrease in fasting insulin of 26%, reflected by an increase in fasting glucose of 11%. The study found evidence for a non-pituitary action of octreotide and has implications for monitoring the treatment of acromegaly patients on octreotide therapy.

Pokrajac, A., Frystyk, J., Flyvbjerg, A., Trainer, P.J. European Journal of Endocrinology 2009, 160: 543-548 DOI: 10.1530/EJE-08-0822