What thyroid hormones cross the placenta?
Maternal thyroxine crosses the placenta in small amounts during the first one-half of pregnancy, when fetal thyroid hormone concentrations are low. The placenta is freely permeable to TRH
TSH levels in term neonates
TSH concentrations increase to 80 mU/L and decrease quickly in the first 24 hours, followed by a slower decrease to less than 10 mU/L after the first postnatal week
Thyrotoxicosis in neonates born to maternal Graves
Between 1% and 5% of offspring will have thyrotoxicosis diagnosed. More than 90% of neonates born at term to mothers with Graves disease may have subclinical thyrotoxicosis
Thyroid levels in moderate preterm in comparison to early preterm
Compared with neonates born at an earlier gestational age, such as at 27 weeks, neonates born at 31 to 34 weeks have higher T4, free T4, and T3 levels. For nenoates born at 31 to 34 weeks gestational age, T4 and T3 levels increase after birth adn peak at 7 hours
Most severe mutations causing hyperinsulinemic hypoglycemia
ABCC8, KCNJ11, which encode the 2 components of pancreatic beta-cell adenosine triphosphate-sensitive potassium channel. These mutations abolish the function of the KATP channel and are therefore unresponsive to diazoxide, a KATP channel agonist
Smith-Lemli-Opitz syndrome
Caused by deficiency of 7-dehydrocholesterol reductase, which results in impaired synthesis of cholesterol. Clinical features are variable but may include cardiac defects, cleft palate, syndactyly, polydactyly, and genital ambiguity. Male patients typically appear phenotypically as female with undescended testes
21-hydroxylase gene
CYP21
Aminophylline
and active metabolite theophylline lead to increased levels of thyroxine and triiodothyronine and less consistently reverse T3
Who would benefit from phosphorus supplementation
Neonates with high TRP levels, low to normal parathyroid hormone levels and hypophosphatemia will benefit from phosphorus supplementation
LH
Critical period for external virilization of the genitalia is within the first 12 weeks of gestation. In the first trimester, testosterone production from the Leydig cells is driven by placental HCG. Fetal pituitary LH secretion increases during the second trimester and stimulates phallic enlargement and testicular descent
thyroid peroxidase
target of antithyroid drugs to inhibit thyroid hormonogenesis
DEXA
Considered the gold standard for assessing bone mineralization and fragility. Normative data and guideliens for use in neonates are lacking. Disadvantages include expense, radiation and possible need for sedation. z-score used to assess bone health
