Endocrine Abstracts

131I-metaiodobenzylguanide (MIBG) therapy, initially introduced in the 1980s, has emerged as a first-line to treatment of malignant phaeochromocytomas. Its other notable use has been in treating neuroblastomas occurring in childhood serving as an adjuvant prior to surgery or chemotherapy. An observed known late consequence of MIBG therapy is Primary ovarian failure (POI), characterised by menstrual irregularities over a period of 4 months associated with high Follicular stimulating hormone (FSH>40 iu/l.) In our study, we conducted a comprehensive review of MIBG therapy within our radionucleotide database, spanning from 2008. Through stringent gender (female) and age (<40) criteria, we identified a subset of 56 patients, ultimately narrowing down to a cohort of 5 patients. Our investigation revealed that 3 out of 5 developed POI consequent to mIBG therapy between 2013 and 2022. The clinical indication was for managing metastatic phaeochromocytoma and paragangliomas. Average age was 35 years. The administered activity of I-131 mIBG during each cycle ranged between 6484-10256 Mbq. Remarkably, 1 patient underwent a single cycle of mIBG, while 1 patient received 2 cycles and another 3 cycles. The onset of oligomenorrhoea, was detected around 4 months following first therapy dose. Subsequent diagnosis of POI was made around 6 months post-treatment. FSH levels at diagnosis were available for 2 patients, measuring 100 IU/l and 85 IU/l. respectively. In conclusion, despite the limited scale of our study, we identified a significant incidence of POI following MIBG therapy. POI is a devastating complication to women of child bearing age. At present patients are not consented about this prior to treatment and such patients are not routinely offered fertility preservation. As renal excretion of the radioisotope is in the bladder, we postulate that introducing intervention, like urinary catheterisation, may mitigate the risk but further research is warranted in this area.