Overview
This lecture explains thyroid storm (thyrotoxic crisis), a life-threatening complication of hyperthyroidism, covering its causes, physiology, symptoms, and management.
Thyroid Hormone Regulation
- The hypothalamus detects low thyroid hormones and releases thyrotropin-releasing hormone (TRH).
- TRH stimulates the anterior pituitary to release thyroid stimulating hormone (TSH).
- TSH acts on the thyroid gland to stimulate production of T3 (triiodothyronine) and T4 (thyroxine).
- T4 is mostly converted to T3 inside cells, which increases basal metabolic rate and activates the sympathetic nervous system.
Causes and Mechanisms of Hyperthyroidism
- Hyperthyroidism is excess thyroid hormone, causing an overall hyper metabolic state.
- Common causes include Graves disease (autoimmune, with antibodies mimicking TSH) and toxic nodular goiter (mutated or overactive follicles).
- Hyperthyroidism results in increased cellular activity, weight loss, heat intolerance, and sympathetic activation.
Thyroid Storm (Thyrotoxic Crisis)
- Thyroid storm is a sudden, severe exacerbation of hyperthyroidism symptoms.
- Possible mechanisms include increased active (unbound) thyroid hormone, heightened tissue sensitivity, or increased response to catecholamines.
- Triggers: surgery, trauma, infection, childbirth, abrupt treatment withdrawal, or excessive hormone intake.
Symptoms and Diagnosis
- Symptoms: severe fever, agitation, confusion, seizures, coma, rapid heart rate, arrhythmias, high-output cardiac failure.
- The difference between thyroid storm and regular hyperthyroidism is symptom severity, not hormone levels.
- Diagnosis is clinical, supported by tests like ECG for arrhythmias.
Treatment and Management
- Immediate intensive care is required.
- Medications: beta blockers, thionamides, iodine preparations, glucocorticoids, bile acid sequestrants.
- In refractory cases, plasmapheresis can remove excess thyroid hormone from the blood.
Key Terms & Definitions
- Thyroid storm — acute, life-threatening worsening of hyperthyroidism symptoms.
- Hyperthyroidism — condition of excessive thyroid hormone production.
- TSH (Thyroid Stimulating Hormone) — pituitary hormone stimulating thyroid hormone release.
- T3 (Triiodothyronine) & T4 (Thyroxine) — thyroid hormones that increase metabolic rate.
- Graves disease — autoimmune disease causing hyperthyroidism.
- Plasmapheresis — blood filtration procedure removing plasma and excess hormones.
Action Items / Next Steps
- Review the regulation and function of the hypothalamic-pituitary-thyroid axis.
- Study treatment protocols for thyroid storm and differentiate from regular hyperthyroidism.