Description

Thyroid disorders in pregnancy can have significant effects on both maternal and fetal health, as thyroid hormones are critical for normal development, particularly of the fetal brain and nervous system. Proper diagnosis and management are essential to ensure a healthy pregnancy. Types of Thyroid Disorders in Pregnancy Hypothyroidism: Insufficient production of thyroid hormones. Common cause: Hashimoto’s thyroiditis (autoimmune). Hyperthyroidism: Excess production of thyroid hormones. Common cause: Graves’ disease (autoimmune). Subclinical Thyroid Disorders: Subclinical hypothyroidism: Elevated TSH with normal free T4. Subclinical hyperthyroidism: Low TSH with normal free T4. Thyroid Nodules or Cancer: Nodules may enlarge during pregnancy, and rare cases of thyroid cancer may be diagnosed. Thyroid Physiology in Pregnancy Increased Demand for Thyroid Hormones: Early pregnancy increases thyroxine-binding globulin (TBG) due to rising estrogen levels. The growing fetus depends on maternal thyroid hormones during the first trimester. Human Chorionic Gonadotropin (hCG): hCG can mildly stimulate the thyroid, leading to a transient decrease in TSH, especially in the first trimester. Hypothyroidism in Pregnancy Causes: Hashimoto’s thyroiditis (autoimmune). Iodine deficiency (rare in developed countries). Symptoms: Fatigue, weight gain, cold intolerance, constipation, dry skin. Severe untreated cases may cause myxedema. Effects on Pregnancy: Increased risk of: Miscarriage and stillbirth. Preeclampsia. Low birth weight. Preterm delivery. Poor fetal brain development due to inadequate thyroid hormone transfer. Diagnosis: Elevated TSH (>4.0 mIU/L in pregnancy). Low free T4. Check thyroid peroxidase antibodies (TPO-Ab) for autoimmune thyroiditis. Management: Levothyroxine (T4): First-line treatment. Adjust dose to achieve trimester-specific TSH targets: 1st trimester: 0.1–2.5 mIU/L. 2nd trimester: 0.2–3.0 mIU/L. 3rd trimester: 0.3–3.0 mIU/L. Monitor TSH every 4–6 weeks. Hyperthyroidism in Pregnancy Causes: Graves’ disease (most common). Gestational transient thyrotoxicosis (due to high hCG levels, often resolves by mid-pregnancy). Symptoms: Palpitations, heat intolerance, weight loss despite good appetite, tremors, goiter, and exophthalmos (in Graves’ disease). Effects on Pregnancy: Increased risk of: Miscarriage, preterm birth. Preeclampsia. Low birth weight. Thyroid storm (life-threatening emergency). Diagnosis: Low TSH (<0.1 mIU/L). Elevated free T4 and/or free T3. Measure TSH receptor antibodies (TRAb) in Graves’ disease. Management: Antithyroid Drugs (ATDs): Propylthiouracil (PTU) in the 1st trimester (less teratogenic). Switch to methimazole (MMI) in the 2nd and 3rd trimesters to reduce hepatotoxicity risk. Monitor free T4 and TSH every 4–6 weeks. Beta-Blockers: For symptomatic control (e.g., propranolol), use with caution and limit duration. Surgery: Rarely needed; thyroidectomy may be considered in severe, refractory cases. Postpartum Thyroiditis Definition: Autoimmune thyroid dysfunction occurring within the first year postpartum. Phases: Hyperthyroid phase: Symptoms like anxiety, palpitations (transient). Hypothyroid phase: Symptoms like fatigue, depression. Treatment: Symptomatic treatment for the hyperthyroid phase. Levothyroxine for the hypothyroid phase if persistent. Monitoring and Follow-Up Pregnancy-Specific TSH Goals: Maintain TSH in trimester-specific ranges to ensure optimal maternal and fetal outcomes. Thyroid Function Tests: Monitor TSH and free T4 every 4–6 weeks during pregnancy and adjust therapy as needed. Fetal Monitoring: In hyperthyroidism, assess for fetal thyrotoxicosis if maternal TRAb levels are elevated. Monitor fetal growth and heart rate. Key Points for Management Adequate iodine intake is essential (250 μg/day in pregnancy). Pre-pregnancy thyroid function optimization is critical, especially for women with known thyroid disease. Avoid radioactive iodine therapy during pregnancy. Prognosis With proper management, most women with thyroid disorders can achieve a healthy pregnancy and deliver a healthy baby.