Final answer:
The pituitary typically enlarges in pregnancy due to increased hormone production, such as thyrotropin, prolactin, and ACTH. Weight gain during pregnancy is primarily in the abdominal region. Fat accounts for a small portion of the weight gain.
Step-by-step explanation:
The pituitary typically enlarges in pregnancy due to increased hormone production. During pregnancy, the anterior pituitary gland produces hormones such as thyrotropin, prolactin, and adrenocorticotropic hormone (ACTH). Thyrotropin increases thyroid hormone production, which raises the maternal metabolic rate. Prolactin stimulates the enlargement of mammary glands for milk production, and ACTH stimulates cortisol secretion for fetal protein synthesis. Additionally, the parathyroid gland increases calcium mobilization from maternal bones for fetal use.
Weight gain is also associated with pregnancy, mainly in the abdominal region. The uterus, amniotic fluid, placenta, and additional breast tissue contribute to this weight gain. However, fat storage only accounts for approximately 2.3 kg (5 lbs) in a normal pregnancy and serves as a reserve for increased breastfeeding demands.