# Thyrotoxicosis With Medullary Thyroid Carcinoma: A Rare Endocrine Diagnostic Challenge

## TL;DR

A rare case of medullary thyroid cancer presenting as hyperthyroidism is reported, highlighting the diagnostic challenge it poses.

## Contribution

This case adds to the limited literature on medullary thyroid carcinoma presenting as thyrotoxicosis.

## Key findings

- A 56-year-old female presented with hyperthyroidism symptoms but was diagnosed with medullary thyroid carcinoma.
- Imaging and FNAC confirmed the presence of high-grade thyroid cancer with lymph node involvement.
- Surgical intervention resolved the patient's symptoms and she remained well at follow-up.

## Abstract

The incidence of a hyper-functioning thyroid gland presenting alongside an underlying malignancy rarely occurs. Herein, we present a rare case of a 56-year-old female patient presenting with features of hyperthyroidism only to be later diagnosed with an underlying malignancy, medullary thyroid carcinoma (MTC). Ultrasonography (USG) of the neck revealed a suspicious nodule with microcalcifications in the right lobe of the thyroid. Subsequent CT imaging of the neck indicated possible cervical and mediastinal lymph node involvement. Fine-needle aspiration cytology (FNAC) confirmed the presence of high-grade thyroid carcinoma. The patient underwent total thyroidectomy with neck node dissection after which her symptoms subsided. She was well at her last follow-up.