ABSTRACT
The epidemiology and natural history of endocrine diseases are such that they commonly occur in women of childbearing age. Endocrine diseases may have adverse consequences for maternal, fetal, and neonatal health; likewise, the pregnancy may alter the expression of endocrine disease and as well may alter the interpretation of diagnostic laboratory testing commonly performed in nongravid patients. Fetal and neonatal hyperthyroidism is caused by placental transfer of maternal thyroid-stimulating immunoglobulins to the fetus. In normal pregnancy, the osmotic thresholds for vasopressin release and thirst are lowered, resulting in plasma osmolality about 10mOsm/kg lower than that in nonpregnant women. Polyuria must not be confused with increased frequency of voiding, which is a common symptom of normal pregnancy. Accurate diagnosis of Cushing's syndrome during pregnancy is difficult based on physiologic changes in cortisol secretion in normal pregnancy. The fetal thyroid begins to take up iodine and synthesize T4 at 10 weeks of gestation.
