Thyroid Hormone and Disorders of Pregnancy Flashcards
describe difference in prevalence of thyroid disorders bw men and women
10x higher in women
what % of women have a subtle form of thyroid disorder
20%
how much do thyroid reqs increase by in preg?
50%
describe hypo -> ant pit _> thyroid hormones
TRH acts on ant pit -> TDH release acting on thyroid -> TH
what proteins are inside the colloid of thyroid follicles?
thyroglobulin (TG) and thyroid peroxidase (TPO)
describe process of TH synthesis
TG is secreted into middle of follicle and iodinated into either T3 (adding 3 iodine) or T4 (adding 4)
what enzyme allows iodination to occur?
thyroid peroxidase
what is the functional form of TH and how is this achieved?
T3 is functional form, T4 has to go through deiodination to become T3
why is T4 important in pregnancy?
T4 can cross placenta but T3 can’t, therefore T4 needed to get into fetal circ where it then goes through deiodination to supply fetus with TH
what mineral in diet important for thyroid and what specific aspects does it assist?
selenium important for deiodination and antioxidants
describe autoimmune cause of thyroid disorder
complex, some damage to thyroid combined with predisposing factor of immune response ignoring self-proteins causing ABs to be made against colloid protein
what amount of iodine intake recommended a day and what amount -> goitre?
100ug/day rec, 50/day =goitre
what are the effects of too much iodine?
damage to thyroid through increased iodination with byproduct of hydrogen peroxide -> reactive iodine = tissue damage and thyroid autoimmunity
what ABs are formed in Hashimoto’s?
ABs against TPO and TG
describe Grave’s disease
too much T4, ABs mimic TSH stimulating TH production = nervousness, weight loss, irreg HR, protruding eyes
when does fetus start making it’s own T4
K20
what is actively transported across placenta to ensure fetal growth and neuro development?
iodine and T4
what amount of iodine intake recommended a day when pregnant and lactating?
150-200ug/day when pregnant and even more when lactating
effect of estrogen on thyroid hormones
estrogen increases thyroid binding globulin which carries TH hormone in the blood -> less unbound T4 allowing reservoir of bound T4 to be transported to fetus
how does hCG affect thyroid hormones in pregnancy?
hCG has similar structure to TSH therefore causes prod of TH, hCG highest for first 11weeks gestation = higher TH = morning sickness
describe gestational thyrotoxicosis and tx
high hCG -> excess T4, not treated unless absolutely medically necessary since drug lowering T4 can cross placenta therefore impact fetal development
describe Grave’s disease effects in preg and tx
can cause miscarriage, LBW, preterm birth, tX with methimazole and PTU but timing is important to avoid abnormalities
describe PP thyroiditis
occurs in 10% of women PP, symptoms may disappear within 12mnths or persist, characterised by abnormal TSH causing hyperthyroid phase as immune suppressing hormones reduce post birth allowing spike in immunity against thyroid
