Introduction: Growth hormone (GH)-deficiency in adults is associated with a range of adverse outcomes that improve with GH replacement. Pituitary adenomas and their treatment account for a large proportion of patients with adult GH-deficiency. However, safety fears have arisen due to the mitogenic effect of excess GH on pre-malignant colonic polyp formation in individuals with acromegaly. This, along with anecdotal suggestions of pituitary tumour recurrence, has prompted further study of the longterm safety of GH replacement.
Patients and Methods: A retrospective observational cohort study of 46 adult patients on GH replacement at our centre, including previous pituitary adenomas, GH-deficiency secondary to therapies for other cancers and young adults with GH-deficiency diagnosed in childhood. Adult GH is titrated to achieve a normal age-related IGF-1. Patients with a previous pituitary adenoma have pituitary scans at 12 year intervals after starting GH. Contemporaneous imaging reports were used and if there was any suspicion of regrowth on these reports, pituitary volumes were calculated by a neuroradiologist using radiotherapy-mapping software.
Results: 5 (10.9%) patients showed an increase in pituitary volume following GH replacement. All had previously been treated by hypophysectomy (three corticotroph adenomas, one prolactinoma, one non-functioning adenoma) and two received pituitary irradiation. Median duration of GH replacement was 1.5 years (modal dose 200 micrograms daily). Mean increase in pituitary volume was 41.7 (SD 35.3)%. Two patients were also found to have increased levels of ACTH. After discontinuing GH, pituitary volume decreased in three patients and remained unchanged in one. For one patient, subsequent volume change could not be calculated as imaging was incompatible with radiotherapy-mapping software.
Discussion: Recurrence rates of pituitary tumours are estimated to be 12% per annum following surgery without radiotherapy. Our results suggest GH therapy may increase that risk and regular scanning of the pituitary remains an important part of follow-up management.
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.