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During pregnancy, immunologic suppression occurs which induces tolerance to the presence of the fetus. [5] Without this suppression, the fetus would be rejected causing miscarriage. [ 5 ] As a result, following delivery, the immune system rebounds causing levels of thyroids antibodies to rise in susceptible women.
Thyroid hormone concentrations in blood are increased in pregnancy, partly due to the high levels of estrogen and due to the weak thyroid stimulating effects of human chorionic gonadotropin (hCG) that acts like TSH. Thyroxine (T4) levels rise from about 6–12 weeks, and peak by mid-gestation; reverse changes are seen with TSH.
TSH levels are determined by a classic negative feedback system in which high levels of T3 and T4 suppress the production of TSH, and low levels of T3 and T4 increase the production of TSH. TSH levels are thus often used by doctors as a screening test, where the first approach is to determine whether TSH is elevated, suppressed, or normal. [25]
Both NTIS and primary hypothyroidism may have reduced fT3 and fT4, and elevated TSH (which is common in the hospital, during the recovery phase of NTIS). [2] Prescribing thyroxine to treat this may lead to lifelong thyroid overtreatment. [2] Hyperthyroidism may be assumed due to decreased TSH and a transient fT4 increase.
Subclinical hypothyroidism, a milder form of hypothyroidism characterized by normal thyroxine levels and an elevated TSH level, is thought to occur in 4.3–8.5% of people in the United States. [8] Subclinical hypothyroidism has been associated with an increased risk of atrial fibrillation (AF) and is the most frequent thyroid abnormality in ...
The thyroid may enlarge slightly in healthy women during pregnancy, but not enough to be felt. These changes do not affect the pregnancy or unborn baby. Yet, untreated thyroid problems can threaten pregnancy and the growing baby. Symptoms of normal pregnancy, like fatigue, can make it easy to overlook thyroid problems in pregnancy. [1]
The diagnosis of hyperthyroidism is confirmed by blood tests that show a decreased thyroid-stimulating hormone (TSH) level and elevated T 4 and T 3 levels. TSH is a hormone made by the pituitary gland in the brain that tells the thyroid gland how much hormone to make. When there is too much thyroid hormone, the TSH will be low.
One factor is an adverse reaction to the hormonal changes of pregnancy, in particular, elevated levels of beta human chorionic gonadotropin (β-hCG). [ 27 ] [ 28 ] This theory would also explain why hyperemesis gravidarum is most frequently encountered in the first trimester (often around 8–12 weeks of gestation), as β-hCG levels are highest ...