Term
| what characterizes changes to the metabolism during pregnancy? |
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Definition
| pregnancy is a hypermetabolic condition, with increased vascularization of organs and a developing fetus with increasing energy demand |
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Term
| how is the increasing energy demand from the fetus compensated for in pregnancy? |
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Definition
| in part by thyroid hormone |
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Term
| what is iodine's relationship to thyroid hormone? |
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Definition
| iodine is the anion which is part of thyroid hormone (T3 = triiodothyronine, T4 = tetraiodothyronine) |
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Term
| why is there increased iodine filtered through the kidney during pregnancy? |
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Definition
| b/c there is increase thyroid hormone production |
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Term
| why is iodine incorporated into prenatal vitamins? |
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Definition
| b/c many pregnant women have a dietary iodine deficiency |
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Term
| how does the placenta interact with thyroid hormone from the mother? |
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Definition
| the placenta is a *barrier for thyroid hormone, and only a very small amount of T4 is transferred from mom -> fetus. (therefore the mother may have profound hypothyroidism, but this will not affect the development of the fetus's thyroid). |
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Term
| why might a pregnant woman present with a goiter? |
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Definition
| this may be due to *increased vascularity of the thyroid gland. often this occurs bilaterally and can be firm or soft. |
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Term
| why are increased *total* T4 and T3 levels in pregnancy not considered hyperthyroidism? |
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Definition
| because thyroid binding globulin (TBG - made in the liver), the major carrier of thyroid hormone in the blood *is increased (peaks at 15-20 wks), therefore - *availability or total T4/3 is increased, but *free T4/3 levels remain the same. |
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Term
| what is the relationship between hCG and TSH? |
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Definition
| hCG and TSH are similar, to the point where placentally produced hCG functions as TSH for the developing fetus during its peak at 10-12 weeks (which correlates with a dip in maternal TSH). |
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Term
| why are declining TSH levels in a pregnant woman not necessarily reflective of hyperthyroidism? |
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Definition
| because when TSH dips in a pregnant woman, placental hCG is performing in its place - a physiologic trading of places. |
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Term
| since maternal T4/3 does not cross the placenta, how does the fetal thyroid develop? |
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Definition
| placental hCG stimulates development of the fetal thyroid (acts as fetal TSH initially), which starts to synthesize its own thyroid hormone at around 12 wks - using iodine from the mother's diet (possible iodine deficiency for mother). at around 20 wks, the fetus is able to produce its own TSH. |
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Term
| what are risks if hypothyroidism in a pregnant pt is not addressed? how can this be addressed? |
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Definition
| pre-eclampsia, gestational HTN, abruption of placenta, anemia, post partum hemorrhage and small for gestational age newborns - the risk for all of which can be lowered by thyroid replacement therapy |
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Term
| with normal thyroid function in a pregnant pt, how might thyroid-antibody positive status affect miscarriage rate? |
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Definition
| thyroid-antibody positive status may increase the miscarriage rate, even w/normal thyroid function |
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Term
| can preterm delivery occur even in subclinical hypothyroidism? |
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Definition
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Term
| what are the risks for a fetus with a mother suffering from hypothyroidism or iodine deficiency? |
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Definition
| normal maternal thyroid function and delivery of dietary iodine are necessary for somatic and neural fetal growth, and if the mother of a fetus has untreated maternal gestational hypothyroidism, the fetus may have reduced cognitive function (infantile hypothyroidism = cretinism). |
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Term
| if the fetus initially develops normal thyroid function but then develops hypothyroidism later on, what are they at risk for? |
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Definition
| lower language development/school performance/motor performance (lower IQ). |
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Term
| who needs to be screened for thyroid dysfunction (particularly in the prenatal context)? |
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Definition
| *every newborn. *women w/a hx of: hyperthyroidism/hypothyroidism, thyroiditis, or thyroid sx. *women with: a fam hx of thyroid disease, goiter, thyroid antibodies, type 1 DM, other autoimmune disorders, infertility (in hypothyroidism, bleeding could be more frequent but they don’t ovulate), hx of miscarriage, preterm delivery. *women w/signs or symptoms of hyper/hypothyroidism (tired, mildly constipated). |
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Term
| what are the instances of thyroid disease in women? |
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Definition
| 1% thyroid disease. 2-3% subclinical hypothyroidism. 10-15% are positive for thyroid antibody (still have higher risk of miscarriage). |
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Term
| what does the etiology for maternal hypothyroidism consist of? |
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Definition
| lymphocytic thyroiditis (hashimoto's - most common in US), post I 131 therapy for grave's disease, and post-thyroidectomy. |
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Term
| how is thyroid dysfunction screened for? |
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Definition
| a free T4 count and an ultrasensitive TSH study. also check: antithyroglobulin antibody and thyroid peroxidase antibody |
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Term
| how is maternal hypothyroidism treated? what characterizes treatment? |
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Definition
| asap w/T4 when detected. thyroxine requirements will increase with pregnancy and therefore adjustments in dosage will need to be evaluated (keep checking levels) and carried out. |
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Term
| what are the recommendations for management of maternal hypothyroidism? |
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Definition
| achieve a TSH of: 0.5-4.0mu/L (2.5-3 is ideal). the mother should take thyroid hormone at least 1/5-2 hrs apart from prenatal vitamin (iron/calcium bind to thyroxine) and TSH levels should be checked at first prenatal visit, then every 4-6 weeks (steady state for thyroid hormone is 5-6 weeks, so this is when you can get thyroid profile again). |
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Term
| what are symptoms of maternal hyperthyroidism? |
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Definition
| usually more clinically apparent than hypothyroidism: nervous/anxious, amenorrhea (still can get pregnant), wt loss (may be normal in 1st trimester), low ultrasensitive TSH test, and tachycardia |
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Term
| what is the etiology of hyperthyroidism? |
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Definition
| graves disease (major cause in pregnant age group w/a nodular, firm goiter), toxic nodules, hydatidiform mole (rare - secretes hCG, can be benign/malignant), thyroiditis, and hyperemesis |
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Term
| how is hyperthyroidism diagnosed? |
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Definition
| low ultrasensitive TSH test, high free T4, and thyroid antibodies |
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Term
| what characterizes graves disease in pregnant pts? |
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Definition
| graves disease may present for the first time in the first trimester of pregnancy or a relapse may occur in the first trimester after a previous remission. graves disease may also exacerbate during pregnancy and/or improve in the third trimester (like other autoimmune disease - may require a dose adjustment). |
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Term
| what are the risks for the infant if a pregnant pt has untreated hyperthyroidism? |
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Definition
| small for gestational age birth, prematurity, stillbirths, and congenital malformation |
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Term
| how is hyperthyroidism in pregnancy treated? |
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Definition
| PTU (propylthiouracil- anti-thyroid hormone synthesis) is first line therapy to reduce thyroid hormone production and elevate TSH levels to ~ 2.5. PTU is also ok for breast feeding mothers. overzealous use of antithyroid therapy can however, cause a fetal goiter (may cross placenta). sx in the 2nd trimester is indicated in uncontrolled situations. |
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Term
| how can grave's disease/hyperthyroidism occur in the fetus or neonate? how is this diagnosed? what is the unique about neonatal grave's disease? |
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Definition
| transplacental transfer of thyroid stimulating immunoglobulin (TSI) to the fetus. TSI antibodies in the mother are evaluated, but the dx is best established w/persistent fetal tachycardia. *neonatal grave's disease is temporary* b/c TSI will ultimately degrade and baby will then have normal thyroid function. |
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Term
| what is postpartum thyroiditis? |
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Definition
| inflammation (not infection, usually painless) of the thyroid gland, which causes release of pre-formed thyroid hormone: initially appearing as hyperthyroid - but this is transient as pre-formed thyroid hormone degrades, shifting to normal hormone levels, then hypothyroid (thyroid may not be making hormone at this point - pt is is fatigued, depressed, withdrawn). *3 phases* |
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Term
| what characterizes incidence of thyroid nodules/CA during pregnancy? |
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Definition
| dx is usually via fine needle aspiration and if CA is confirmed, it is usually papillary (can wait for sx until after delivery). if sx (thyroidectomy) is necessary (invasive), it is usually done in the 2nd trimester. |
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Term
| are thyroid scans performed in pregnancy? |
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Definition
| no - radioactive iodine should not be given to a pregnant pt (always do pregnancy test before running). US can be done. |
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Term
| how should antithyroid medication (PTU) be administered to a pregnant pt in need of it? |
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Definition
| minimal amounts, just enough to normalize TSH levels (PTU has a very short half life - so need to take 3-4x/day) |
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Term
| how much should iodine intake increase in pregnancy? |
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Definition
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