Thyroid Flashcards
what are adverse outcomes associated with thyroid disorders
- miscarriage, fetal loss
- gestational hypertension, pre-eclampsia
- intrauterine growth restriction [IUGR]
- compromised fetal neurocognitive development
- fetal distress
- stillbirth
- premature birth
- lactation difficulty
- postnatal depression
- thyroid storm
- maternal congestive heart failure
normal production of thyroid hormones [T3 and T4] is dependent on
- an adequate supply of dietary iodine
- a normally functioning thyroid gland
- a functioning pituitary gland producing adequate TSH
- a functioning hypothalamus producing adequate TRH
where is iodine found
in seafood, vegetables grown in iodine-rich soil, and iodized table salt.
clinical picture of hyperthyroidism [high T3 and T4]
- increased basal metabolic rate
- weight loss with good appetite
- anxiety, physical restlessness, nervousness, excessively emotional
- hair loss
- fast pulse, heart palpitations
- intolerance to heat, warm sweaty skin
- diarrhea
- exophthalmos [protrusion of the eyes] in Graves’ disease
- oligomenorrhea or amenorrhea
what is the clinical presentation of hypothyroidism [low T3 and T4]
- decreased basal metabolic rate
- weight gain and poor appetite. easily fatigues
- mental sluggishness, depression, lethargy, psychosis
- dry skin, brittle hair
- slow, weak pulse
- dry cold skin, poor tolerance to cold. puffy appearance on face hands and feet [myxedema]
- constipation
- anovulation
what are some of the changes to maternal thyroid function in pregnancy
- a marked increase of TBG
- Increased T3 and T4
fetal requirements for thyroid hormone in first trimester - increased demand for iodine
- hCG has a thyroid- stimulating effect
- de-iodination of thyroid hormones in the placenta to facilitate passage of iodine to the fetus
- thyroid function tests are difficult to interpret
What thyroid hormone crosses the placenta
iodine crosses the placenta and thyroxine [T4] is transferred, but only in the 1st trimester. T3 and TSH do not cross at all
when does the fetal thyroid begin functioning
at the end of the 1st trimester, and prior to that the fetal brain development is dependent on maternal supply of T4, which is converted intracellularly to T3. during this time thyroid hormones are most important to fetal brain development.
what is fetal intellectual development dependent on
adequate amounts of thyroid hormone. Deficiencies can lead to impaired growth and irreversible intellectual disability.
what happens in women with severe iodine deficiency during pregnancy
trapping mechanisms override fetal demand, conserving iodine for maternal use but this results in congenital iodine deficiency syndrome [poor growth and intellectual deficiency ]
why might hCG cause transient biochemical hyperthyroidism
hCG and TSH share a similar structure and have similar receptors, giving hCG thyroid-stimulating features. hCG stimulates the thyroid gland during early pg. In situations with high hCG like multi-fetal pg, molar pg, and HG hCG may overstimulate the TSH receptors causing the transient hyperthyroidism
what is the thyroid activity in labor and birth
the levels of total and free T3 increase in response to the increase energy requirement of the contracting uterine muscles.
what happens to the thyroid during pp
delivery of placenta and consequent reduction in estrogen, the production of TBG decreases, as does the renal excretion of iodine. gradually over 4-6 weeks the changes to thyroid function of pg are reversed.
when is the diagnosis of thyroid disorders ideal
pre-conception as some diagnostic tools and treatments are inadvisable in pg
how can hyperthyroidism affect pregnancy
lead to hypertensive disease of pg, cardiac disease, infection, IUGR, stillbirth, abruption or preterm labor, and thyroid storms
what is a thyroid storm
or thyrotoxin crisis is a rare but acute and life threatening event. presents with variety of serious symptoms- pyrexia, agitation, confusion, tachycardia [and fetal tachycardia], and congestive heart failure. predisposing factors labor and delivery and infections/ trauma in those with less well controlled
what if hyperthyroidism present first during pregnancy
thyrotoxicosis usually occurs in late first or early second trimester and can be hard to diagnose because many of s/s are common during pg
what is the typical care/ treatment for those with hyperthyroidism during pg
regular blood tests to assess thyroid function in pg [and probably an increased number for those newly diagnosed]. about 30 percent of women can discontinue their medications towards the end of pg as the immune suppressive effect of pg leads to reduced antibody levels
what increased risk is there with the fetus [hyperthyroidism]
risk of fetal thyrotoxicosis, may be suspected during antepartum with persistent fetal tachycardia [170] and confirmed on u/s [fetal goiter with or without IUGR]. if suspected needs carful higher monitoring as an increased fetal mortality rate has been identified as wel as other complications.
what to consider pp with hyperthyroidism
- cord blood should be taken at delivery to test neonatal thyroid function, and pediatrician should be informed.
- abnormal maternal thyroid hormone levels can impact milk letdown and can affect breastfeeding
what is the main cause of hypothyroidism worldwide
iodine deficiency
iodine deficiency is the most common cause of what
preventable intellectual and developmental disability known as congenital iodine deficiency syndrome
what is them most common cause of hypothyroidism in developed countries
result of autoimmune destruction of thyroid tissue. Atrophic autoimmune thyroiditis and Hashimoto’s thyroiditis [chronic autoimmune thyroiditis ]
What are some risks with hypothyroidism
miscarriage, pre-eclampsia, abruption, low birth weight, stillbirth, and preterm birth, and increased rates of gestational hypertension and rarely myxedema coma
what to keep in mind in pp with hypothyroidism
may predispose to postnatal depression
what is postpartum thyroiditis
an inflammatory autoimmune disorder. onset usually is usually within the first few months postnatal. most women progress through hyperthyroidism and hypothyroidism, then symptoms spontaneously resolve usually within 12 months. symptoms may include depression and memory impairment, together with ‘classical’ symptoms such as heat/cold intolerance, fatigue and palpitations
