Autoimmune Thyroid Disease-Postpartum Thyroiditis
Certain disease affecting the function of the thyroid gland occur when and individuals immune system fails to recognize particular thyroid proteins as ‘self’ and reacts to the proteins as if they are foreign. The usually triggers both humoral and cellular immune responses. As a result, antibodies to these proteins are generated, which then alter thyroid function. Two common autoimmune diseases with opposite effects on thyroid function are Hashimoto’s disease and Grave’s disease. In Hashimoto’s disease, the thyroid gland is infiltrated by lymphocytes and elevated levels of antibodies against several components of thyroid tissue (e.g.’ antithyroid peroxidase and antithyroglobulin antibodies) are found in the serum. The thyroid gland is destroyed, resulting hypothyroidism. In Grave’s disease, stimulatory antibodies to the TSH receptor activate thyroid hormone synthesis, resulting in hyperthyroidism.
A third, fairly common autoimmune disease is postpartum thyroiditis, which usually occurs within 3 to 12 months after delivery. The disease is characterized by a transient thyrotoxicosis (hyperthyroidism) often followed by a period of hypothyroidism lasting several months. Many patients eventually return to the euthyroid state (normal state).Often only the hypothyroid phase of the disease may be observed, occurring in more the 30% of women with antibodies to thyroid peroxidase detectable preconception. The disease is also observed in patients known to have Grave’s disease. The postpartum occurrence of the disorder is likely due to increase immune system function following the suppression of its activity during pregnancy.
It has been estimated that 5 to 10% of women develop postpartum thyroiditis. Of these women, about 50% have transient thyrotoxicosis alone, 25% have transient hypothyroidism alone, and the remaining 25% have both phase of the disease. The prevalence of the disease has prompted a clinical recommendation suggesting that thyroid function (serum T4, T3 and TSH levels) be surveyed postpartum at 2, 4, 6, and 12 months in all women with thyroid peroxides antibodies or symptoms suggestive of thyroid dysfunction. Patients who have experienced one episode of postpartum thyroiditis should also be considered at risk for recurrence after pregnancy.
Treatment for thyrotoxicosis commonly involves inhibiting thyroid hormone synthesis and secretion. Thionamides are a class of drugs that inhibit the oxidation and organic binding of thyroid iodide to reduce thyroid hormone production. Some drugs like propylthiouracil inhibit the conversion of T4 to T3 in the peripheral tissues. Thyroid hormone replacement is required to treat hypothyroidism.
References:
- Harrison’s Principles of Internal Medicine, 17th edition.
- Davidson’s Principles and Practice of Medicine, 20th Edition
- The Washington Manual of surgery, 5th edition.
- Medical physiology, Lippincott Williams & Wilkins 3rd edi.
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