# Incidental detection of multiple endocrine neoplasia and medullary thyroid carcinoma before starting GLP-1 agonist: A case report

## TL;DR

A man was diagnosed with a rare inherited endocrine condition before starting a weight-loss medication, leading to thyroid cancer surgery.

## Contribution

Highlights the importance of screening for endocrine neoplasia before GLP-1 agonist use.

## Key findings

- Elevated calcitonin and CEA levels led to the detection of medullary thyroid carcinoma.
- Genetic testing confirmed a germline RET mutation consistent with multiple endocrine neoplasia 2A.
- Early diagnosis allowed successful treatment and family screening.

## Abstract

A man, in his 30s, with a history of obesity and hypothyroidism planned to begin taking a new Glucagon-like peptide-1 (GLP-1) agonist for weight loss. As these medications have been associated with C-cell hyperplasia, a calcitonin level was checked as evaluation prior to starting the drug. This returned at 131 pg/mL (upper limit of normal<10 pg/mL), and a subsequent carcinoembryonic antigen was 5.2 ng/mL (ref<3 ng/mL). Thyroid ultrasound was performed and demonstrated bilateral subcentimeter nodules. After total thyroidectomy, final pathology demonstrated bilateral 0.8 cm medullary thyroid carcinoma. Genetic testing revealed a NM_020975.6: c.1826G > A; p.Cys609Tyr. germline RET mutation, confirming the diagnosis of multiple endocrine neoplasia 2 syndrome. The patient recovered well from treatment. His first-degree relatives also underwent genetic testing. This case represents a surprising diagnosis of familial multiple endocrine neoplasia 2A prior to starting a Glucagon-like peptide-1 agonist.