Pregnancy and Lactation Physiology

During lactation, which hormone is responsible for the milk letdown (milk ejection) reflex?

A 28-year-old primigravida at 32 weeks gestation presents to the antenatal clinic with complaints of severe heartburn and constipation. On examination, she has a gravid uterus consistent with her gestational age. Her blood pressure is 118/76 mmHg. She asks why her digestive symptoms have worsened despite taking antacids. Which of the following hormonal changes during pregnancy is primarily responsible for her gastrointestinal symptoms?

A 32-year-old multiparous woman delivers a healthy 3.2 kg male infant vaginally at term. On postpartum day 3, she reports severe bilateral breast pain, engorgement, and a low-grade fever (38.2°C). On examination, both breasts are tense, swollen, and warm. She has not yet initiated breastfeeding. Her serum prolactin level is 180 ng/mL (normal non-pregnant: 5–25 ng/mL). Which of the following best explains the physiological basis of her current clinical presentation?

Which hormone is primarily responsible for maintaining the corpus luteum during the first 8 weeks of pregnancy?