Chapter 101 The Endocrine System

The endocrinopathies are discussed in detail in Part XXVI.

Pituitary dwarfism is not usually apparent at birth, although male infants with panhypopituitarism may have neonatal hypoglycemia, hyperbilirubinemia, and micropenis. Conversely, constitutional dwarfs usually have length and weight suggestive of prematurity when born after a normal gestational period; otherwise, their physical appearance is normal.

Primary hypothyroidism occurs in approximately 1/4,000 births (Chapter 559). Because most infants with serious and treatable disease are asymptomatic at birth, all states screen for it. Thyroid deficiency may also be apparent at birth in genetically determined cretinism or in infants of mothers treated with antithyroid medications or during a pregnancy complicated by maternal hyperthyroidism. Constipation, prolonged jaundice, goiter, lethargy, or poor peripheral circulation as shown by persistently mottled skin or cold extremities should suggest cretinism. Early diagnosis and treatment of congenital thyroid hormone deficiency improve intellectual outcome and are facilitated by screening of all newborn infants for this deficiency.

Transient hypothyroxinemia of prematurity is most common in ill and very premature infants. These infants are probably chemically euthyroid, as suggested by normal levels of serum thyrotropin and other tests of the pituitary-hypothalamic axis. Because the relationship between low thyroid levels and neurodevelopmental outcome is unclear, it remains uncertain whether premature infants with this transient problem should be treated with thyroid hormone.

Transient hyperthyroidism may occur at birth in infants of mothers with hyperthyroidism or in infants whose mothers have been receiving thyroid medication.

Transient hypoparathyroidism may manifest as tetany of the newborn (Chapter 565).

The adrenal glands are subject to numerous disturbances, which may become apparent and require lifesaving treatment during the neonatal period. Acute adrenal hemorrhage and failure may occur after breech or other traumatic deliveries or in association with overwhelming infection. Signs of adrenal insufficiency and shock can occur. Congenital adrenal hyperplasia is suggested by vomiting, diarrhea, dehydration, hyperkalemia, hyponatremia, shock, ambiguous genitals, or clitoral enlargement. Some infants have ambiguous genitals and hypertension. Because the condition is genetically determined, newborn siblings of patients with the salt-losing variety of adrenocortical hyperplasia should be closely observed for manifestations of adrenal insufficiency. Newborn screening and early diagnosis and therapy for this disorder may prevent severe salt wasting and adverse outcomes. Congenitally hypoplastic adrenal glands may also give rise to adrenal insufficiency during the 1st few weeks of life.

Female infants with webbing of the neck, lymphangiectatic edema, hypoplasia of the nipples, cutis laxa, low hairline at the nape of the neck, low-set ears, high-arched palate, deformities of the nails, cubitus valgus, and other anomalies should be suspected of having gonadal dysgenesis.

Transient diabetes mellitus (Chapter 583) is rare and is encountered only in newborns. It usually manifests as dehydration, loss of weight, or acidosis in infants who are small for gestational age.

101.1 Infants of Diabetic Mothers

Waldemar A. Carlo

Women with diabetes in pregnancy (type 1, type 2, and gestational) are at increased risk for adverse pregnancy outcomes. Adequate glycemic control before and during pregnancy is crucial to improving outcome.

Diabetic mothers have a high incidence of polyhydramnios, preeclampsia, pyelonephritis, preterm labor, and chronic hypertension; their fetal mortality rate is greater than that of nondiabetic mothers, especially after 32 wk of gestation. Fetal loss throughout pregnancy is associated with poorly controlled maternal diabetes (especially ketoacidosis) and congenital anomalies. Most infants born to diabetic mothers are large for gestational age. If the diabetes is complicated by vascular disease, infants may be growth restricted, especially those born after 37 wk of gestation. The neonatal mortality rate is >5 times that of infants of nondiabetic mothers and is higher at all gestational ages and in every birthweight for gestational age category.

Pathophysiology

The probable pathogenic sequence is that maternal hyperglycemia causes fetal hyperglycemia, and the fetal pancreatic response leads to fetal hyperinsulinemia; fetal hyperinsulinemia and hyperglycemia then cause increased hepatic glucose uptake and glycogen synthesis, accelerated lipogenesis, and augmented protein synthesis (Fig. 101-1). Related pathologic findings are hypertrophy and hyperplasia of the pancreatic islet β cells, increased weight of the placenta and infant organs except for the brain, myocardial hypertrophy, increased amount of cytoplasm in liver cells, and extramedullary hematopoiesis. Hyperinsulinism and hyperglycemia produce fetal acidosis, which may result in an increased rate of stillbirth. Separation of the placenta at birth suddenly interrupts glucose infusion into the neonate without a proportional effect on the hyperinsulinism, and hypoglycemia and attenuated lipolysis develop during the first hours after birth.