Endocrine Abstracts (2012) 28 MTE3

Preventing and managing long term complications of acromegaly

Karim Meeran

Department of Medicine, Imperial College London, London, United Kingdom.

The treatment of Acromegaly includes radiotherapy, surgery, and medical treatment to reduce GH levels. The aim of treatment is to reduce GH levels to a “safe” level. The secretion of GH in normal individuals is pulsatile, so that most normal people have concentrations of GH close to zero for most of the time, with concentrations rising to about 6 ng/ml three or ten times per day (approx 20 mU/l). The height and frequency of these GH peaks is variable. However because the levels are mostly very low, the total area under the curve of GH is low, and is represented by IGF-1. Tumours that secrete GH usually do not demonstrate pulsatile secretion, to the area under the curve of GH and the IGF-1 can be vastly increased. Completely removing the tumour but not removing the normal pituitary at all would be the ideal outcome. However to ensure removal of as much of a macroadenoma as possible, some normal pituitary may be either deliberately or inadvertently removed. Total hypophysectomy will result in GH deficiency as well as deficiency of cortisol, thyroxine and sex steroids, and possibly ADH. GH and other hormone deficiencies are also associated with increased morbidity and occasionally mortality. The aim of treatment is thus to restore the pituitary to normal. However any remaining tumour might make very little GH, but still result in a raised IGF-1 because the area under the curve will be much higher than when levels are close to zero. There can thus be discordance between GH levels and IGF-1 levels following pituitary surgery, radiotherapy and drug treatment. Early guidelines suggested that the aim of treatment was to reduce the GH level to about 5.0 ng/ml. The target for GH levels have thus been dropping over the years. Until the late 1990s, the suggested “safe” level was 5 mU/l (about 1.7 ng/ml), but the consensus guidelines in the year 2000 redefined remission to a GH suppressed to less than 1.0 ng/ml (about 3 mU/l) with a normal IGF-1 level. More recently the target has dropped further to 0.4 ng/ml during an OGTT. The relative merits of random GH level measurements, or levels during a day curve and levels during an OGTT together with the IGF-1 depends on which treatment modalities have been used.

Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.

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