Endocrine Abstracts

A 71 year old obese lady was noticed to have acromegalic facies and bilateral carpal tunnel syndrome, increasing ring and shoe size, but no sweats or headaches. Random IGF-1 was raised (39.1nanomol per litre). Following oral glucose tolerance test (OGTT) fasting glucose was normal but impaired at 2hours (4.8 and 9.6millimol per litre respectively), growth hormone (GH) suppressed from a baseline of 3.8microunits per litre to 2.2microunits per litre. Following thyrotropin releasing hormone (TRH), GH rose (GH at 0, 20 and 60minutes was 3.4, 8.7 and 24.4microunits per litre respectively). Thus treatment with cabergoline was initiated. IGF-1 remained elevated, cabergoline was stopped and GH re-measured. The mean GH of 8 samples taken over 4 hours was 2.4microunits per litre. IGF-1 remained high (49.2nanomol per litre) and IGFBP-3 raised (4.8milligram per litre). TRH test remained abnormal. MRI showed a microadenoma on the right of the pituitary. The patient refused surgery or radiotherapy. Current treatment with cabergoline has reduced but not normalised her IGF-1.

In 1979 GH suppression following OGTT below 4microunits per litre was considered normal. In 1993 OGTT GH suppression below 2microunits per litre and mean GH on frequent sampling below 5microunits per litre was shown to normalise mortality rates. Diabetes presents further difficulties with false positive GH response to OGTT, usually however IGF-1 is low. In 2002 a series of patients had normal OGTT GH suppression, but raised IGF-1 and pituitary adenoma on MRI. Surgery resulted in normalisation of IGF-1 and decrease in GH levels. Further long term prospective studies are needed to clarify the outcome benefits of treatment in such circumstances.