Endocrine Abstracts

Background: Approximately 10% of primary hyperparathyroidism (PHPT) cases are due to inherited germline pathogenic variants. Historically, genetic testing was recommended for people developing PHPT under 35 years, or for individuals under 45 with other risk factors for inherited disease (family history of PHPT, multigland disease or hyperplasia, presence of other syndromic features). The NHS England National Genomic Test Directory testing criteria have been updated to extend genetic testing to individuals developing PHPT under 50 years without additional risk factors for inherited disease.

Aim: To determine the yield of additional syndromic PHPT diagnoses in individuals with PHPT between 35-50 years where FHH (familial hypocalciuric hypercalcaemia) had been excluded biochemically (urinary fractional calcium excretion of >0.01).

Method: We identified individuals age 35-50 years, who had had surgery for PHPT in the past 5 years and identified those who had not been offered genetic testing at the time of their surgery. We contacted them by letter with the option to ‘opt in’ to genetic testing. Individuals opting in had a telephone consultation to discuss genetic testing and to obtain informed consent. Blood samples were sent for genetic testing and results obtained.

Results: 61 individuals age 35 to 50 had undergone parathyroidectomy for PHPT. 9 had undergone genetic testing on clinical grounds (1 case of MEN-1 identified). 52 individuals were sent an opt in letter. 26 (50%) responded to the invitation (21/26 (81%) by email and 5/26 (19%) by post). Following a telephone consultation, all 26 consented for genetic testing and 26/26 (100%) genetic test results were negative.

Conclusions: We did not identify any pathogenic variants in 26 individuals undergoing genetic testing for PHPT age 35-50 years, where FHH had been excluded and other risk factors were not present. The yield of genetic testing in this age group is likely to be low.