7.9. Endocrinology of pregnancy, delivery, and lactation. Flashcards
I. Pregnancy
1. What is pregnancy?
- When an ovum is fertilized by a sperm, the fertilized ovum begins to divide and then develop into a fetus.
- The following period is defined as pregnancy and lasts about 40 weeks.
I. Pregnancy
2. What happen during pregnancy?
During pregnancy – estrogen and progesterone levels increase as their functions include maintenance of the endometrium, development of the breasts for lactation, and suppression of the new ovarian follicles from maturation.
I. Pregnancy
3. What happen in 3 trimesters?
- In first trimester – the hormonal source is the corpus luteum.
- In last two trimesters – the placenta is the major producer of hormones maintaining
the pregnancy.
II. Fertilization
1. What happen during Preparation to fertilization?
Ovary in the late follicular stage produces high levels of estrogen
- Promotes endometrium growth
- Induces expression of the progesterone receptor
- (+)-feedback to LH -> LH surge -> resumption of meiosis -> ovulation
II. Fertilization
2. What happen during fertilization?
- Upon ovulation, ovum is surrounded by corona radiata -> arrives to fallopian tube
- Egg is trapped in the isthmus (neck), where fertilization takes place
- The motility of ciliae + SM oviduct have to migrate the fertilized egg to the uterus
- Arrives at the uterus around day 4-5, as a blastocyst
II. Fertilization - cellular events of fertilization
3A. What are cellular events of fertilization?
II. Fertilization - cellular events of fertilization
3B. What happen in step 2 “enetration of the zona pellucida by the sperm”?
- Acrosomal pattern: release of acrosomal enzymes induced by binding of the sperm to the zona protein ZP3
- ↑[Ca2+]IC triggers fusion of the outer acrosomal membrane with the cell membrane of the spermexocytosis of the acrosomal contents
II. Fertilization - cellular events of fertilization
3B. What happen in step 2 “enetration of the zona pellucida by the sperm”?
- Acrosomal pattern: release of acrosomal enzymes induced by binding of the sperm to the zona protein ZP3
- ↑[Ca2+]IC triggers fusion of the outer acrosomal membrane with the cell membrane of the spermexocytosis of the acrosomal contents
II. Fertilization - cellular events of fertilization
3C. What happen in step 3 “Cortical reaction occurs”?
3) Cortical reaction occurs ( -> prevents polyspermy)
- ↑[Ca2+]IC triggers exocytosis of cortical granules, which contain enzymes
- ↑[Ca2+]IC induces completion of oocyte’s meiosis 2
II. Fertilization - cellular events of fertilization
3D. What happen in step 4 “Sperm enters the egg”?
- The nucleus of the mature ovum is now called the female pronucleus
- The sperm nucleus decondenses and then transforms into the male pronucleus
II. Fertilization - cellular events of fertilization
3E. What happen in step 5 “Zygote forms”?
5) Zygotes forms as the male and female pronuclei fuse
- Zygote bears 46 chromosomes (23 maternal + paternal chromosomes)
III. Implantation
1. What happen during implantation?
III. Implantation
2. What is the Maternal response to implantation?
- Pre-decidualization + decidualization (stromal cells become enlarged + rounded decidual cells)
- Decidua forms an adhesive epithelial sheet -> inhibits migration of the implanting embryo
III. Implantation
3. What are the 3 areas of decidua?
1) Decidua basalis
2) Decidua capsularis
3) Decidua parietalis
III. Implantation
4. What is decidua basalis?
The area underneath the implanting embryo
III. Implantation
5. What is decidua capsularis?
the area overlies the embryo
III. Implantation
6. What is decidua parietalis?
The area covering the remainder of uterine surface
IV. Placenta
1. What are the sites of placenta circulation?
V. Placental hormone secretion
1. What is Maternal-placental fetal unit?
joint effort of steroid synthesis by the mother and fetus during pregnancy
V. Placental hormone secretion
2. What are the 2 hormones participating in Placental hormone secretion?
- Human chorionic gonadotropin (hCG)
- Human chorionic somatomammotropins (hCS)
V. Placental hormone secretion
3. What are the features of Human chorionic gonadotropin (hCG)?
- Maintenance of corpus luteum (progesterone and estrogen production)
- Helps male fetus to produce testosterone
- Its presence is a key factor for determining pregnancy (found in urine)
- May activate TSH receptors -> hyperthyroidism
V. Placental hormone secretion
4. What are the features of hCS?
- Unrequired for fetal growth, but triggers changes in the maternal body during pregnancy
- Stimulates mammary gland growth
- Stimulates production of the fetal growth- promoting hormones
VI. Steroid hormone synthesis during pregnancy
1. What happen in Steroid hormone synthesis during pregnancy?
During pregnancy, maternal levels of progesterone and estrogens (estradiol, estrone, estriol) increase and reach concentration higher than those achieved during a normal menstrual cycle
VI. Steroid hormone synthesis during pregnancy
2. What are the 2 synthesized hormones during pregnancy?
- Estrogens
- Progesterone
VI. Steroid hormone synthesis during pregnancy
3. What is the role of estrogens?
Estrogens (estradiol most prominent in pregnant women):
- Promotes cellular division
- Enlargement of uterus
- Enlargement of breast and growth of ducts
- Enlargement of external genitalia
- Relax pelvic ligaments
VI. Steroid hormone synthesis during pregnancy
4. What is the role of Progesterone?
- Prevents menstruation
- Decidual cell maintenance
- Inhibition of uterine contractions
- Helps to prepare the breasts
VII. Maternal-placental fetal unit
1. What is Maternal-placental fetal unit?
Joint effort of steroid synthesis by the mother and fetus during pregnancy
VII. Maternal-placental fetal unit
2. How is Progesterone synthesized?
- Synthesized in placenta (syncytiotrophoblast) from cholesterol.
- Syncytiotrophoblast do not have CYP17 = cannot produce androgens (estradiol) -> need androgen precursor from fetus.
VII. Maternal-placental fetal unit
2. How is Estrogen synthesized?
- Has CYP17
- DHEA(S) is produced in the fetal adrenal gland from cholesterol (from ACTH)
- DHEA(S) will go to the placenta, where it produces testosterone -> estrone + estradiol
- DHEA(S) will also go to the fetal liver, where it undergoes hydroxylation (CYP3A7) to 16(OH)-DHEA(S) -> will go to placenta and produce estriol
=> By measuring the estriol level of the mother, it can give some information of the fetal liver and the ‘’well-being’’ of the fetus
VIII. Metabolic changes
1. What are metabolic changes during pregnancy?
Prolactin (PRL) and hCS (also known as hPL) will lead to anti-insulin action -> decreased maternal glucose use:
- additional glucose availability for the fetus
- lipolysis + proteolysisfatty acids for maternal
use + AAs for fetus
VIII. Metabolic changes
2. Why is pregnancy pro-diabetic?
Because of the anti-insulin actions: pregnancy is pro diabetic => gestational diabetes can appear when decreased glucose tolerance can be seen
VIII. Metabolic changes
3. Make a schematic diagram of metabolic changes
IX. Cardiorespiratory changes
1. What are cardiorespiratory changes?
X. Delivery
1. What is the role of fetus during delivery?
- Fetus is responsible for initiation of labor, can be because of ischemic episodes in
placenta/fetus. - Cortisol also plays an important role in initiation of labor together with prostaglandins
X. Delivery
2. What happen in placenta during delivery?
In the placenta, because of this stress situation, CRH is produced together with ACTH
-> androgen↑
-> ratio of [E]/[P4]↑
-> number of oxytocin receptors, gap junction nd α-AR ↑ in myometrium
X. Delivery
3A. What do Decidua and myometrium do during delivery?
Decidua and myometrium will produce PGF2α, together with oxytocin, will cause contractions of myometrium
=> Ferguson reflex:
- Fetus head pushed towards vagina
-> cervix + vagina stretches
-> oxytocin release
-> ‘’relaxing’’ of uterus + stretching, so fetus can come out
X. Delivery
3B. What happen in Ferguson reflex?
Ferguson reflex:
- Fetus head pushed towards vagina
-> cervix + vagina stretches
-> oxytocin release
-> ‘’relaxing’’ of uterus + stretching, so fetus can come out
X. Delivery
4. What is the role of oxytocin?
Oxytocin will also cause vasoconstriction at the site where the placenta used to be, reducing blood loss
X. Delivery
5. Make a schematic diagram of delivery
X. Delivery
6. Give a summary of 3 stages of delivery
1st stage: onset of true labor by release of maternal oxytocin -> associated by Ferguson reflex
2nd stage: further dilation of cervix and continues until the delivery of the baby
3rd stage: delivery of the placenta
XI. Mammogenesis and lactation
1. What are Secretory units of the breast?
Secretory units of the breast are the alveoli contained in a secretory tube
XI. Mammogenesis and lactation
2. What does the breast consist?
- The breast consists of secretory lobules, which empty into ductules
- 15-20 ductules combine into a duct, which leads to the ampulla
- The lactiferous duct carries the product out
XI. Mammogenesis and lactation
3A. What are the 4 hormones that affect the breast?
XI. Mammogenesis and lactation
3A. What are the 4 hormones that affect the breast?
XI. Mammogenesis and lactation
4. What are the 4 steps of milk secretion?
1) Secretory pathway
- Proteins are made in the ER
- Ions (Ca2+, Pi) and lactose are added in the Golgi
- H2O enters the vesicle via osmosis
- Contents are discharged via exocytosis
2) Transcellular exocytosis and endocytosis of immunoglobulins
3) Lipid is secreted in apocrine manner
4) Transcellular/ paracellular salt and H2O transport
XII. Nursing
1. What are the 4 steps of nursing?
- Stimulus from suckling travels from breast, through spinal cord to the HT
- Neurons from spinal cord inhibit dopamine release from the arcuate nucleus
- This reflex also activates production of oxytocin => contraction of myoepithelial cells for ejection of milk
- So actually, suckling does not force ejection of milk from breast, but the action of SMCs does eject the milk - Afferent input from the nipple inhibits the release of GnRH
XII. Nursing
2. What happen in step 2 “Neurons from spinal cord inhibit dopamine release from the arcuate nucleus”?
- ↓dopamine removes the inhibition of dopamine on lactotrophs
- ↑prolactin release -> prolactin stimulates milk production in the breast
XII. Nursing
3. What happen in step 4 “Afferent input from the nipple inhibits the release of GnRH”?
- ↓GnRH -> ↓LH + FSH = preventing ovulation
- During breastfeeding the possibility of ovulation decreases, however, in
humans this effect is not very pronounced -> women can get pregnant after 1 month of labor
XIII. Birth control pills
2. What is the role of birth control pills?
