Date post: | 17-Dec-2015 |
Category: |
Documents |
Upload: | thomasina-shepherd |
View: | 220 times |
Download: | 0 times |
Overt hypothyroidism complicates up to 3 of 1,000 pregnancies
Subclinical hypothyroidism is estimated to be 2-5 % (Canaris GH, 2000)
In Macau, around 2-3% (rough estimation)
Hypothalamus releases TRH
Act on the pituitary gland to release TSH
TSH causes the thyroid gland to release the thyroid hormones (T3 and T4)
TRH and TSH concentrations are inversely related to T3 and T4 concentrations.
•99% circulating T3 and T4 is bound to TBG. 1% free form Biologically
Active
Aboubakr Elnashar
Developed Countries Hashimoto’s thyroiditis – Chronic thyroiditis prone to develop postpartum thyroiditis
Worldwide Iodine deficiency (Rare in Macau)Other Causes:
◦ Subacute thyroiditis -> not associated with goiter◦ Thyroidectomy, radioactive iodine treatment
An inflammatory disorder of thyroid glands More common on those with other
autoimmune diseases Almost 100% associated with anti-TPO
antibody. (Fitzpatrick & Russell) May cause transient hyperthyroidism
PE: Goiter, rubbery consistency, moderate in size, mostly bilateral, painless.
T cells recognize the patient’s own thyroid antigens as foreign
cytotoxic to thyroid epithelial cells stimulate B cells to make anti-thyroid
antibodies, anti-peroxidase antibody, anti-thyroglobulin antibody, and anti-TSH-receptor antibody
block the action of TSH, leading to hypothyroidism!!
Affect 38% of worldwide population (Pearce EN, 2008)
Sources: Iodized salt and seafood. Others: cow milk, egg, beans…
Perinatal mortality Congenital cretinism (growth failure, mental
retardation, other neuropsychological deficits)
ACOG
Average intake 250 µg/d Urine iodine > 150 µg/d Diana L. Fitzaptrick 2007
Subacute granulomatous thyroiditis - Painful - Fever, myalgia - Viral infection Subacute lymphocytic thyroiditis - includes postpartum thyroiditis
(Prevalent: 5% ) - PainlessSymptomatic Tx for initial hyperthyroidism
Elevated TSH (> 3.0 mIU/l) with normal FT4, FT3.
31 % with anti-TPO antibody (Casey BM, 2007)
More common on women with autoimmune diseases
50 % hypothyroidism in 8 years May cause childhood IQ decrease Increase in preterm 4% vs 2.5% in
euthyroid mother (Casey BM, 2007)
<1% hypothyroidism cases
Low or normal serum TSH concentrations + low serum T4 and T3
2nd (TSH deficiency) hypothyroidism: - pituitary tumor - postpartum pituitary necrosis (Sheehan's syndrome) - trauma, infiltrative diseases.
3rd (TRH deficiency) hypothyroidism can be caused by - Damages the hypothalamus or - Interferes with hypothalamic-pituitary portal blood flow
Slowing of metabolic processes:Lethargy/fatigue weight gain cognitive dysfunctioncold intolerance constipation bradycardiadelayed relaxation of tendon reflexesslow movement and slow speech
Deposition of matrix substances:Dry skin hoarseness edemapuffy face and eyebrow loss peri-orbital edemaenlargement of the tongue
OthersDecreased hearing myalgia and paresthesia depressionmenorrhagia arthralgia pubertal delaygalactorrhea
Symptoms Hypothyroidism Pregnancy
Fatigue
Constipation
Hair Loss
Dry Skin
Brittle Nail
Weight Gain
Fluid Retention
Bradycardia
Carpel Tunnel Syndrome
Pregnancy is a state of relative iodine deficiency, because:
- Active transport to fetoplacental unit - Increase iodine excretion in urine, 2 fold (increased GFT & decreased renal tubular reabsorption)
- Thyroid gland increases its uptake from the blood
TBG - Increase (hepatic synthesis is increased)
TT4 & TT3 - Increase to compensate for this rise
FT4 & FT3 (crosses the placenta in the 1st half of pregnancy)
- Decrease. FT4 are altered less by pregnancy, but do fall little in the 2nd & 3rd trimesters.
TSH (does not cross placenta)
- decreases in 1st trimester, between 8 to 14 wks HCG, HCG has thyrotropin-like activity - Increase in 2nd & 3rd trimester (Increased TBG)
Overt hypothyroidism in pregnancy is rare
In continuing pregnancies hypothyroidism is associated with increased risk of:
◦ Pre-eclampsia◦ Placenta Abruption◦ increased c-section rates◦ Fetal death (especially if increased TSH occurs
in 2nd trimester) Motherisk April 2007
Maternal thyroid hormones are important in embryogenesis
No production until 12 weeks, therefore needs mom’s T4 for fetal brain development
Maternal hypothyroidism can cause negative effect on fetal intellectual development.
Higher incidence of LBW (due to medically indicated preterm delivery, pre-eclampsia, abruption)
Iodine deficient hypothyroidism -> congenital cretinism (growth failure, mental retardation, other neuropsychological deficits)
Motherisk April 2007, CMAJ Apr 2007 176(8)
Treatment before 10 weeks’ gestation No adverse effect
Family Hx of autoimmune thyroid disease Women on thyroid therapy Presence of goiter or thyroid nodules Hx of thyroid surgery Infertility Unexplained anemia or hyponatremia or high
cholesterol level Previous Hx of - neck radiation - postpartum thyroid dysfunction - previous birth of infant with thyroid problem Other autoimmune chronic conditions: Type 1 DM
Overt hypothyroidism: symptomatic patient elevated TSH level low levels of FT4 and FT3
Subclinical hypothyroidism: asymptomatic patient elevated TSH normal FT4 and FT3
Replacement with external thyroid hormone -- levothyroxine (Levothyroid, Levoxyl, Synthroid, and Unithroid).
Levothyroxine (Synthroid) pregnancy category A
◦ A sterioisomer of physiologic thyroxine◦ 1.6 mcg/kg, ◦ usually about 50 to 100 mcg/day for women◦ 30-60 minutes before eating breakfast.
The American Association of Clinical Endocrinologists recommends keeping the thyroid-stimulating hormone (TSH) level between 0.3 and 3.0 mIU/L.
After readjustment of levothyroxine, observe 6-8 weeks
Check TSH every trimester
Rapid or irregular heartbeat Chest pain or shortness of breath Muscle weakness Nervousness Irritability Sleeplessness Tremors Change in appetite Weight loss
Safe in pregnancy and lactation Very little thyroxin crosses the placenta NO risk of thyrotoxicosis of fetus
Patients who were on thyroxine therapy before pregnancy should increase the dose by 30% once pregnancy is confirmed (Bombrys et al, 2008)
Keep TSH level between 0.3 and 3.0 mU/L.
TSH should be monitored every trimester until delivery.