Leucine aminopeptidase is a proteolytic liver enzyme whose serum levels may be increased with liver disease. Its activity is markedly elevated in pregnant women. he rise, however, results from a pregnancy-speciic enzyme(s) with distinct substrate speciicities (Song, 1968). Pregnancy-induced aminopeptidase has oxytocinase and vasopressinase activity that occasionally causes transient diabetes insipidus.
During normal pregnancy, gallbladder contractility is reduced and leads to greater residual volume (Braverman, 1980). Progesterone potentially impairs gallbladder contraction by inhibiting cholecystokinin-mediated smooth muscle stimulation, which is the primary regulator of gallbladder contraction. Impaired emptying, subsequent stasis, and the increased cholesterol saturation of bile in pregnancy contribute to the increased prevalence of cholesterol gallstones in multiparas. In one study, approximately 8 percent of women had gallbladder sludge or stones when imaged at 18 and/or 36 weeks' gestation (Ko, 2014).
he pregnancy efects on maternal serum bile acid concentrations are still incompletely characterized. his is despite the long-acknowledged propensity for pregnancy to cause intrahepatic cholestasis and pruritus gravidarum from retained bile salts. Cholestasis of pregnancy is described in Chapter 55 (p. 1059).
During normal pregnancy, the pUUltary gland enlarges by approximately 135 percent (Gonzalez, 1988). This increase may suiciently compress the optic chiasma to reduce visual fields.
Impaired vision from this is rare and usually due to macro ad enomas (Lee, 2014). Pituitary enlargement is primarily caused by estrogen-stimulated hypertrophy and hyperplasia of the lactotrophs (Feldt-Rasmussen, 2011). And, as discussed subse quently, maternal serum prolactin levels parallel the increasing size. Gonadotrophs decline in number, and corticotrophs and thyrotrophs remain constant. Somatotrophs are generally sup pressed due to negative feedback by the placental production of growth hormone.
Peak pituitary size may reach 12 mm in MR images in the irst days postpartum. he gland then involutes rapidly and sen, 2011). he incidence of pituitary prolactinomas is not increased during pregnancy (Scheithauer, 1990). When these tumors are large before pregnancy-a macroadenoma measur ing : 1 0 mm-then growth during pregnancy is more likely (Chap. 58, p. 1132).
he maternal pituitary gland is not essential for pregnancy maintenance. Many women have undergone hypophysectomy, completed pregnancy successfully, and entered spontaneous labor while receiving compensatory glucocorticoids, thyroid hormone, and vasopressin.
During the first trimester, growth hormone is secreted predominantly from the maternal pituitary gland, and concentrations in serum and amnionic luid lie within the nonpregnant range of 0.5 to 7.5 ng/mL (Kletzky, 1985). As early as 6 weeks' gestation, growth hormone secreted from the placenta becomes detectable, and by approximately 20 weeks, the placenta is the principal source of growth hormone secretion (Perez-Ibave, 2014). Maternal serum values rise slowly from approximately 3.5 ng/mL at 10 weeks to plateau at about 14 ng/mL after 28 weeks. Growth hormone in amnionic fluid peaks at 14 to 15 weeks and slowly declines thereafter to reach baseline values after 36 weeks.