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Endocrine Abstracts (2016) 44 S1.1 | DOI: 10.1530/endoabs.44.S1.1

SFEBES2016 Symposia Challenges in pituitary disease (3 abstracts)

How to manage patients with acromegaly and discordant GH and IGF-I results

Peter Trainer


Manchester.


Serum GH and IGF-I levels are closely correlated but discordance between GH and IGF-I levels can occur in patients with acromegaly either as a consequence of biological factors or as an artefact of the means of assessment or definitions of normality.

Pegvisomant as a GH receptor antagonist lowers serum IGF-I but, due to negative feedback, increases GH levels. Raloxifene has been shown to lower IGF-I in men and women with acromegaly and oestrogen has been described as the ‘poor woman’s pegvisomant’ because it induces a state of relative GH resistance. In our studies in women with untreated acromegaly, serum IGF-I was 82 ng/ml lower than men, with the difference being 130 ng/ml in women on oral oestrogens. Mean IGF-I was 14 ng/ml lower in men with acromegaly on testosterone therapy, presumably a consequence of aromatisation. Increasing age was associated with a fall in IGF-I, for a given GH level.

Pituitary radiotherapy results in apparent discordance between GH & IGF-I levels as the former declines faster than the latter. Pulsatility studies indicate that circulating IGF-I values correlate most closely with trough, rather than mean or peak, GH values. As >70% of circulating IGF-I is hepatic in origin, liver disease can result in impaired IGF-I generation.

A plethora of consensus statements and guidelines on the management of acromegaly have been published in the last 15 years resulting in regular revisions of the biochemical criteria of the goals of therapy. However vigilance is required when applying international criteria to local practice, as bias in assay performance can be significant, a problem compounded by quality assurance concerns with some commercial kits. Furthermore, the commendable trend to use several thousand samples to define reference ranges has resulted in a significant lowering of the upper limit of reference ranges for IGF-I, such that a patient regarded as controlled by IGF-I criteria a decade ago may no longer be so.

When GH & IGF-I levels are grossly elevated the factors described above are of little clinical relevance. The true challenge of discordant results is in the patient with nearly ideal control and who may benefit from additional treatment. In an era of ever-greater technology, seeking symptoms from patients remains critical to management and good outcomes.

Volume 44

Society for Endocrinology BES 2016

Brighton, UK
07 Nov 2016 - 09 Nov 2016

Society for Endocrinology 

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