Hypothyroidism, a condition characterized by insufficient thyroid hormone production, has diverse etiologies and impacts multiple body systems. This article provides a detailed overview based on the uploaded document.
Causes of Hypothyroidism
1. Iodine Deficiency: The most common cause worldwide. A lack of iodine disrupts thyroid hormone synthesis.
2. Autoimmune Disorders:
Hashimoto’s Thyroiditis: The leading cause in iodine-sufficient regions. Autoimmune antibodies like Anti-TPO and Anti-TG attack thyroid tissue. It is associated with genetic predispositions (e.g., HLA DR-3, HLA DR-4).
IgG4-Related Thyroiditis (Riedel’s): A rare autoimmune condition linked to other fibrotic diseases like retroperitoneal fibrosis.
3. Postpartum Thyroiditis: Often transient, occurring within a year after delivery.
4. Infectious and Viral Causes:
De Quervain’s Thyroiditis: Painful thyroid inflammation following a viral upper respiratory tract infection.
5. Iatrogenic Causes: Medical interventions like thyroidectomy, radioactive iodine therapy, or medications (e.g., amiodarone).
6. Secondary Hypothyroidism: Due to pituitary dysfunction leading to reduced TSH.
Types of Hypothyroidism
1. Primary Hypothyroidism:
- Direct thyroid dysfunction.
- Elevated TSH and reduced T3/T4 levels.
2. Secondary Hypothyroidism:
Caused by pituitary disorders (e.g., Sheehan Syndrome, pituitary adenomas).
Clinical Manifestations
1. Classic Symptoms:
Weight gain, lethargy, cold intolerance, and constipation.
2. Neurological Dysfunction:
Delayed deep tendon reflexes, confusion, and in severe cases, myxedema coma.
3. Cardiovascular Dysfunction:
Bradycardia, diastolic hypertension, and potential heart failure in myxedema coma.
4. Integumentary Signs:
Pretibial myxedema, periorbital edema, and dry skin due to water retention in glycosaminoglycans (GAGs).
5. Reproductive Dysfunction:
Menstrual irregularities, infertility, and reduced libido.
6. Metabolic Dysfunction:
Hyperlipidemia caused by reduced LDL receptor sensitivity.
Myxedema Coma: A Life-Threatening Complication
1. Precipitating Factors:
Infection, surgery, cold exposure, or noncompliance with levothyroxine therapy.
2. Key Features:
Hypothermia, severe bradycardia, and coma.
3. Pathophysiology:
Profound thyroid hormone deficiency reduces metabolic activity and cardiac output, exacerbating hypothermia and fluid retention.
Diagnosis and Management
1. Laboratory Evaluation:
- Elevated TSH and low T3/T4 in primary hypothyroidism.
- Reduced or normal TSH with low T3/T4 in secondary cases.
2. Management:
- Levothyroxine: Standard treatment to replace T4.
- Monitoring: Regular TSH assessments to adjust dosage.
- Myxedema Coma: Immediate hospitalization, intravenous levothyroxine, and supportive care (e.g., warming, electrolyte correction).
