Endocrine Abstracts

A 35 year-old lady presented with classical acromegaly. Headache was a significant feature of her presentation. An oral glucose tolerance test (OGTT) confirmed acromegaly, with growth hormone (GH) levels of 21.6, 21.5, 27.0, 25.0 and 24.7 mU/l at 0, 30, 60, 90 and 120 minutes respectively. A large pituitary tumour invading the left cavernous sinus was found. Trans-sphenoidal hypophysectomy lowered GH levels but did not provide biochemical cure (10.2, 7.2, 8.1, 9.6, 9.3 mU/l). Because the patient was still symptomatic, she underwent trans-cranial surgery and radiotherapy. Octreotide 100 microgrammes was given for symptomatic relief, the latter providing immediate analgesia in terms of headache. Octreotide was so effective for her left-sided headache that she increased the frequency of injections to above the recommended 3 per day. Although octreotide alleviated headache in every instance, the length of analgesic effect gradually reduced until the patient found herself taking up to 12 injections per day. A severe rebound headache was experienced if she missed out the octreotide. Despite an OGTT showing biochemical cure of her acromegaly (mean GH <0.5 mU/l) octreotide remained effective for her headache. The analgesic effect of octreotide was confirmed in a double-blinded placebo-controlled manner. Octreotide-dependency was diagnosed, and the patient was admitted for withdrawal of the drug. The patient continues to experience persistent left-sided headache, although is no longer dependent upon octreotide.

This case gives two important teaching points. Firstly, octreotide appears to have an analgesic effect in pituitary tumours even in the absence of active growth hormone secretion. Secondly, octreotide dependency is a potential complication of therapy. Somatostatin is known to act on both opiate and somatostatin receptors, and up-regulation of these receptors may be the involved in this phenomenon