![]() ![]() Ĭentral hypothyroidism is of pituitary or hypothalamic origin. In subclinical hypothyroidism, TSH levels are elevated, and free T4 levels are normal. In overt hypothyroidism, TSH levels are elevated, and free T4 levels are low. Serum TSH level is used to screen for primary hypothyroidism in most patients. Hashimoto disease is difficult to differentiate clinically however, some features are specific for this condition such as: Patients can also present with carpal tunnel syndrome, sleep apnea, hyponatremia, hypercholesterolemia, congestive heart failure, and prolonged QT interval. Rarely patients can present with ascites, rhabdomyolysis, and pericardial effusion. Symptoms of depression, anxiety, psychosis, cognitive impairments such as memory loss can be present. History of adverse pregnancy and neonatal outcomes should also be sought. Also obtain a complete medical, surgical, medication, and family history. Inquire about dry skin, voice changes, hair loss, constipation, fatigue, muscle cramps, cold intolerance, sleep disturbances, menstrual cycle abnormalities, weight gain, and galactorrhea. Typical features such as cold intolerance, puffiness, decreased sweating and skin changes may not be present always. It is important to maintain a high index of suspicion for hypothyroidism since the signs and symptoms can be mild and nonspecific and different symptoms may be present in different patients. The decline in the production of T4 results in an increase in the secretion of TSH by the pituitary gland, causing hypertrophy and hyperplasia of the thyroid parenchyma, thereby leading to increased T3 production. Alteration in the structure and function of any of these organs or pathways can result in hypothyroidism. Levels of T3 majorly and T4, to some extent, in turn, exert negative feedback on the production of TRH and TSH. The half-life of T4 is 7-10 days, and eventually, T4 is converted to T3 peripherally by 5'-deiodination. Thyroid-stimulating hormone stimulates the thyroid gland to produce and secrete mainly T4 (approximately 100-125 nmol daily) and smaller quantities of T3. The hypothalamus secretes thyrotropin-releasing hormone (TRH) that stimulates the pituitary gland to produce thyroid-stimulating hormone (TSH). The most common cause of hypothyroidism is the inability of the thyroid gland to produce a sufficient amount of thyroid hormone however, less commonly pituitary and hypothalamus may also result in thyroid dysfunction. Secondary and tertiary hypothyroidism, also known as central hypothyroidism is caused by a defect in the hypothalamic-pituitary axis. Its causes include the following: It commonly occurs in middle-aged women and is usually a self-limiting disease.Īutoimmune polyendocrinopathy type-1 results from a mutation in the AIRE gene and is a constellation of Addison disease, hypoparathyroidism, and mucocutaneous candidiasis. Radiation treatment to the head and neck area can also result in hypothyroidism.Ī relatively uncommon cause of primary hypothyroidism is subacute granulomatous thyroiditis, also known as de Quervain disease. The use of radioactive iodine to manage Grave disease usually results in permanent hypothyroidism in about 80-90% of the patients within 8-20 weeks after treatment. However, some women are at high risk for permanent hypothyroidism or recurrent postpartum thyroiditis in future pregnancies. ![]() ![]() Only a few women require treatment with thyroid hormone. Postpartum thyroiditis affects nearly 10% of women and often presents 8-20 weeks after the delivery of the infant. A new class of cancer medications such as anti- CTLA- 4 and anti- PD- L1/ PD- 1 therapy has been associated with both primary and/or secondary hypothyroidism. ![]()
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