PERMANENT HYPOTHYROIDISM DEVELOPS IN 30% PATIENTS.
IT IS A VARIANT OF HASHIMOTO THYROIDITIS & IS CHARACTERIZED BY THE PRESENCE OF ANTIMICROSOMAL ANTIBODIES.
THERE ARE THREE STAGES OF PRESENTATIONS :
1. HYPERTHYROIDISM WHEN THERE IS INITIAL DSTRUCTION OF THE GLAND CAUSING RELEASE OF THYROID HORMONES IN CIRCULATION
2. HYPOTHYROIDISM
3. RESOLUTION OR EUTHYROID STAGE
THE TREATMENT DEPENDS ON THE STAGE OF THE GLAND.
Hyperthyroidism: The goal of treatment is to maintain clinical euthyroidism, with the mother's FT4 level in the high-normal range.
Thioamide drugs (antithyroid drugs [ATDs]) are the first-line treatment in pregnancy. PTU, methimazole (MMI), and carbimazole (CMI) are the ATDs available in the United States. These drugs inhibit iodination of thyroglobulin and thyroglobulin synthesis by competing with iodine for the enzyme peroxidase. PTU and MMI or CMI are equally effective. PTU has not been associated with fetal scalp defects, aplastic cutis, or choanal atresia. Therefore, PTU tends to be the first choice in this class of drugs. ATDs should be maintained at the lowest dose needed to keep the mother's FT4 level in the high-normal range. Weight gain, pulse rate, FT4, and thyrotropin should be monitored monthly.
Beta-blockers (eg, atenolol, nadolol, propranolol) are a valuable adjunct to ATDs. These drugs effectively alleviate symptoms of hypermetabolic states. With prolonged use, beta-blockers are associated with fetal morbidity; therefore, these drugs should only be used for a short period (ie, 2 wk), while waiting for the ATDs to take effect.
Iodide decreases serum T4 and T3 levels by 30-50% in 10 days. Iodide is used in combination with ATDs and beta-blockers during the preoperative treatment of patients with hyperthyroidism. Iodide can also be used in the medical treatment of patients with thyroid storm. Fetal hypothyroidism resulting from placental passage is reported with prolonged use of iodide products; therefore, iodide use should be limited to less than 2 weeks.
Radioactive iodine is contraindicated in pregnancy.
Hypothyroidism: The goal of treatment is to normalize maternal thyrotropin levels.
Thyroid hormone replacement is the treatment for patients with hypothyroidism. A full replacement dose should be instituted at the time of diagnosis.
Patients with subclinical hypothyroidism should be treated to normalize maternal thyrotropin levels.
In general, the thyroid hormone requirement increases approximately 50% during pregnancy; therefore, the thyrotropin level should be monitored closely. Serum thyrotropin levels should be measured 4-6 weeks after each change in T4 dosage.
Surgical Care:
Hyperthyroidism
Subtotal thyroidectomy, for reasons that remain unclear, induces remission in most patients with Graves disease. Surgery should be used as the second line of treatment in pregnant patients.
Surgery is reserved for those patients who meet one of the following criteria:
High doses of ATDs (PTU >300 mg, MMI >20 mg) required
Inability to control clinical hyperthyroidism
Fetal hypothyroidism occurring at dose needed for maternal control
Inability to tolerate ATDs
Noncompliance
Suspected malignancy
When surgery is needed, it should be performed during the second trimester.
Hypothyroidism: No surgical care is recommended.
DRUG TREATMENT :
1. ANTITHYROID DRUGS :
- PROPYLTHIOURACIL
- METHIMAZOLE
2. IODIDES :
- IODIDE
3. THYRID HORMONES
- LEVOTHYROXINE
4. BETA BLOCKERS :
- ATENOLOL
- PROPRANOLOL