# Late-Onset Thyroid Hormone Resistance Following Total Thyroidectomy for Papillary Thyroid Cancer

## TL;DR

A patient with a history of thyroid cancer and multiple endocrine disorders developed thyroid hormone resistance after a thyroidectomy, highlighting the challenges in diagnosing this rare condition.

## Contribution

This case report presents a rare instance of late-onset thyroid hormone resistance following thyroidectomy and multiple comorbidities.

## Key findings

- The patient exhibited elevated TSH levels despite high-dose levothyroxine, suggesting thyroid hormone resistance.
- The case underscores the difficulty in diagnosing RTH in patients with complex medical histories.
- It highlights the importance of considering RTH in patients with atypical endocrine symptoms and prior thyroidectomy.

## Abstract

Thyroid hormone resistance (RTH) is a rare disorder characterized by impaired cellular responsiveness to thyroid hormones, leading to discordant thyroid function tests and varied clinical manifestations. We present the case of a 43-year-old Cuban-American female patient who presented with dizziness, vertigo, repeated falls, and a severe headache following a minor fall. Additional symptoms included nausea, vomiting, photophobia, cold intolerance, generalized body aches, and fatigue. Her medical history was significant for total thyroidectomy for papillary thyroid cancer, multiple sclerosis (MS), pituitary macroadenoma, Cushing’s disease, and polycystic ovary syndrome (PCOS). Post-thyroidectomy, she remained on high-dose levothyroxine (400-750 mcg daily). However, laboratory tests showed persistently elevated thyroid-stimulating hormone (TSH) levels, hence raising suspicion for RTH.

This case highlights the challenges of diagnosing and managing RTH, a rare endocrine disorder often resulting from mutations in the thyroid hormone receptor-beta (THB) gene. RTH is characterized by inappropriately normal or elevated TSH despite high thyroid hormone levels, reflecting tissue-level resistance. This case underscores the complexities of identifying RTH in the setting of multiple comorbidities and a history of thyroidectomy. It also emphasizes the need for clinician awareness of atypical presentations of RTH, particularly in patients with extensive endocrine and systemic histories.