Chapter 13- Estrogens and progestins

Infundibulum

Finger-like projections in contact with ovary and controlled by estrogen

Uterus

Perimetrium is thin lining lost during menstruation, estrogen is primarily responsible for growth of myometrium (smooth muscle layer) during pregnancy

Cervix

Protects uterine contents, rigidity caused by progesterone and softening by estrogen

Vagina

Fibroelastic tissue and smooth muscle with mucous membrane, estrogen

Ovary

Produces and releases ovum, site of biosynthesis and secretion of progesterone and estrogen

Estrogen antagonists

Selective estrogen receptor modulators

Progesterone antagonists

Selective progesterone receptor modulators, blocks p4 leading to abortion

Progesterone synthesis

Corpus luteum produces progesterone, steroidogenesis is dependent on stimulation of cholesterol side chain cleavage

Hypothalamic pituitary ovary axis

Hormones here control the cycles of follicle development, ovulation, and preparation of uterine endometrium for implantation

Follicular phase

LH target cells (thecal cells) and FSH target cells(granulosa cells), at the end of follicular, granulosa cells also express LH receptor in preparation for ovulation

Luteal phase

LH stimulates P4 and E2 which leads to negative feedback on LH and FSH release and inhibits kisspeptin secretion

Follistatin

Binds to and blocks the effect of activin

Inhibins

Inhibit FSH secretion by blocking activin binding to its receptor

Ovulation

Release of ovum from follicle with LH surge, meiosis temporarily resumes, and prostaglandin E2 synthase is synthesized to breakdown the follicle wall

Luteal phase

Granulosa and thecal cells become vascularized CL, LH induces luteinization and P4 is produced for CL growth and preparation for implantation but regresses with PGF2a stimulation into corpus albicans

Secretory phase

Increase thickness of endometrium, secretion of glycogen and uterine gland molecules, increased vascularization and formation of spiral arteries

Estrogen receptor

Two forms alpha and beta, from separate genes and their expression in distribution differs

Binding of estrogen to receptor

Leads to homodimerization and binding to DNA response elements affect gene expression

Progesterone receptors

PR-A can act as a repressor of PR-B and for estrogen and androgen receptors, act as transcriptional regulatory proteins

Estrogen dominance during proliferative phase

Preparation of uterus to respond to P4 by increasing mRNA transcription of ERa and PR, stimulates TGFB, EGF and VEGF

Progesterone dominance during secretory phase

Required for ovulation, fertilization, and differentiation of cells of the endocrine glands needed for implantation, limits effectiveness of estrogen on growth of endometrium

Effects of progesterone and estrogen on bone

Skeletal sexual dimorphism, peak bone mass, closure of epiphyseal growth plate, mineral homeostasis during reproduction to build bone in the fetus, maintenance of bone mass

Estrogen and cardiovascular system

Vasorelaxation via eNOS stimulation, inhibition of vascular smooth muscle proliferation and inhibits apoptosis and necrosis of myocardial cells