Endocrinology of reproduction half of pregnancy, progesterone and prolactin prepare the mammary glands for lactation. Estrogens and progesterone promote mammary epithelial cell proliferation resulting in the formation of the primary and secondary ductal structure. Progesterone induces formation of tertiary side-branches in the mammary glands during puberty and during the luteal phase of the menstrual cycle upon which lobuloalveolar structures form under the influence of prolactin. Prolactin stimulates lactogenesis. hCG appears to be soporific during pregnancy; levels of hCG correlate with sleep changes during pregnancy, and administration of hCG increases sleep in rats likely via neuronal LHCGR. Endocrinology of reproduction Hormonal regulation occurs at
Menstrual cycle of the menstrual cycle, regardless of fertility. Behavior towards potential mating partners changes during different phases of the menstrual cycle. Near ovulation, women may have increased physical attraction and interest in attending social gatherings with men. During the fertile phase of the cycle, women appear to prefer males who are more masculine. The intensity of mate guarding differs across the phases of the cycle, with increased mate guarding occurring when woman are fertile. During the fertile phase, many women experience more attraction, fantasies and sexual interest for extra pair men but not for the primary partner. They also engage in