Thyrotoxicosis: Clinical Presentation, Diagnosis, and Complications

Symptoms and Pathophysiology

Thyrotoxicosis produces heightened adrenergic activity—manifested by tachycardia, palpitations, anxiety, tremor, and neuro‑psychiatric changes—along with weight loss, heat intolerance, and other systemic effects; cardiovascular manifestations are the most severe and potentially life‑threatening. [@1]
Excess thyroid hormone raises tissue thermogenesis and basal metabolic rate while lowering systemic vascular resistance, with the greatest impact on the cardiovascular system. [@3]
The severity of clinical manifestations correlates only moderately with serum thyroid hormone concentrations, so patients with similar laboratory values may exhibit widely different symptom burdens. [@1]
Younger individuals and patients with larger goiters tend to experience more intense adrenergic symptoms such as tachycardia and tremor. [@1]

Atrial fibrillation is a frequent and serious complication of untreated thyrotoxicosis, increasing the risk of embolic events and mortality. [@1]
Persistent tachycardia and increased cardiac workload can progress to heart failure, contributing to the high morbidity associated with the disease. [@1]
Untreated disease is linked to osteoporosis, embolic phenomena, cardiovascular collapse, and overall increased mortality. [@1]

Overt thyrotoxicosis is defined by a suppressed thyroid‑stimulating hormone (TSH < 0.01 mU/L) together with elevated free thyroxine (T4) and/or triiodothyronine (T3). [@1]
“T3‑toxicosis” (isolated elevation of T3 with normal T4) characterizes early disease or autonomous nodular thyroid tissue. [@1]

The American College of Endocrinology and the American Association of Clinical Endocrinologists recommend that evaluation focus first on cardiovascular and neuromuscular complications, as these determine the patient’s morbidity and mortality risk and guide therapeutic decisions. [@1]

Patients typically present with moderate‑to‑severe anterior neck pain radiating to the ears, jaw, or throat, accompanied by exquisite thyroid tenderness. [@4]
The acute phase is often associated with low‑grade fever, generalized malaise, marked fatigue, and myalgias, distinguishing it from painless, insidious autoimmune thyroiditis. [@4]

Markedly elevated erythrocyte sedimentation rate (ESR) and C‑reactive protein (CRP) together with mild anemia are characteristic laboratory findings. [@4]
Thyroid‑specific autoantibodies (anti‑TPO, anti‑thyroglobulin) are typically absent in viral thyroiditis but are present in approximately 75 % of autoimmune thyroid disease cases. [@4]