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

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.

Keywords: delayed presentation; genetic mutations in thyroid hormone signaling; hyperthyroxinemia with normal tsh; thyroid cancer treatment outcomes; thyroid hormone resistance (rth).

Figure 1. Baseline electrocardiogram (EKG) showing sinus bradycardia with a heart rate of 41 bpm (red box)

Figure 2. (A-C) Brain CT without intravenous contrast agents. No CT evidence of acute intracranial hemorrhage, midline shift, or mass effect

CT: computed tomography

Figure 3. Abdominal CT without contrast. Shows small anterior pelvic soft tissue contusion (red circle), but no other intra-abdominal/adrenal or intrapelvic abnormalities

CT: computed tomography

Figure 4. Transverse (A) and anterior-posterior (B) CT chest without intravenous contrast showing no acute cardiopulmonary disease. No definite focal lesions in the thyroid gland region (red arrow)

CT: computed tomography

Figure 5. Echocardiogram during hospital admission showed moderate concentric left ventricular hypertrophy and preserved left ventricular ejection fraction (LVEF) (red box)

Figure 6. Abdominal ultrasound showed mild hepatomegaly and increased liver echogenicity, which was suspected to represent hepatic steatosis (yellow outline)