Puberty, pregnancy, & menopause Flashcards
Age of onset of puberty (boys vs girls)
- Girls: 8-13
- Boys: 9-14
Define puberty
Maturation of HPG axis
- Initiation of pulsatile GnRH release
- Appearance of secondary sex characteristics
- Acceleration of growth
- Capacity for fertilization
Gonadotropic secretion in fetus
- FSH & LH levels rise at midgestation then fall
- Pregnancy hormones exert negative feedback
Gonadotropic secretion upon delivery
- Source of negative feedback removed
- Gonadotropin levels rise but then negative feedback occurs, until puberty
Normal pubertal development in girls
- Thelarche = start of puberty
- Pubarche
- Pubertal maturation complete in 2 yrs
- Menarche (by 13th bday)
- Adipose tissues around hips
Normal pubertal development in boys
- Increase in testicular size, development of pubic hair, penile enlargement = start of puberty
- Facial & body hair increases.
- Muscle bulk increases.
- Adult testicular volume & penile size achieved by 16 yo
- Voice deepens as larynx enlarges.
- Final height at 18 yo
Growth spurt
GH, IGF-1
- Girls: begins in early puberty, peak velocity attained by menarche
- Boys: begins near end of puberty, almost 2 years later than girls
Gonadotropin-independent precocious puberty
Hypogonadotropic hypergonadism
- FSH, LH, GnRH levels decreased
- Sex steroids increased
- Problem tends to be within gonads
Gonadotropin-dependent precocious puberty
Hypergonadotropic hypergonadism
- FSH, LH, GnRH levels increased
- Sex steroids increased
- Early increase in growth.
- Doesn’t follow usual progression
- Most serious side effect: short stature
Constitutional delay
- Lack of physical maturation 2 SD beyond mean age of pubertal onset
- Benign variant of normal
- Progression pattern is normal but delayed
Hypogonadotropic hypogonadism
Deficiency of pulsatile release of gonadotropins
- FSH, LH, GnRH levels decreased
- Sex steroids decreased
- Ex. Kallman’s syndrome
Hypergonadotropic hypogonadism
- Primary gonadal failure FSH, LH, GnRH levels increased Sex steroids decreased - Absence of negative feedback *Ex. Turner's syndrome: - Functional gonads do not form
Pubertal trigger: Leptin
- Leptin receptor in hypothalamus
- Leptin fxns as a permissive factor, not a trigger, in onset of human puberty
- Larger % of adipocytes = larger amount of leptin (potential for early puberty)
4 stages of pregnancy
- Initiation
- Maintenance
- Parturition
- Lactation
Stage 1: Initiation entry
- Sperm are viable up to 72 hrs
- Ova are fertile for 12-24 hrs
- Process of capacitation or “activation” occurs
Stage 1: Initiation cervix
- Sperm motility in the cervical canal requires alkaline pH
- Alkaline secretions from prostate gland elevate pH
- Estrogen: watery mucus facilitating sperm
Initiation: Implantation
- Fertilized ovum stays in the oviduct & undergoes mitosis
- Progesterone secreted by corpus luteum converts uterus to secretory gland
- Secretes glycogen & lipid required for implantation
- Relaxes the myometrium
Blastocyst is composed of what 2 cell types?
- Trophoblast cells:
microvilli of these cells interdigitate w/ endometrium - Inner cell mass:
cells destined to become embryonic structures
How many days does it take for a blastocyst to implant in the uterine wall?
6-8 days after fertilization
- Day 20-24 of menstrual cycle
By day 10, trophoblasts form what layers?
- Cytotrophoblasts (inner layer):
Release hypothalamic-like peptides (CRH, GnRH, TRH) - Syncytiotrophoblasts (outer layer):
Release pituitary-like peptides (ACTH, hCG)
*Principal site of placental steroid & protein hormone biosynthesis
Placenta is essential for…
- Vital fetal fxn
- Maintaining pregnancy
Placenta fxns
- Nutritive
- Excretory
- Immunological
- Barrier
- Respiratory
Role of hCG
- In early pregnancy, hCG rescues corpus luteum & maintains progesterone production until placental steroidogenesis is established
- Stimulates Leydig cells of male fetus to make testosterone along w/ fetal pituitary gonadotropins
- Suppresses maternal immune function & reduces possible rejection
When do hCG levels peak?
60-70 days
- Then remains low for rest of pregnancy
Stage 2: Preparation for implantation
LH stimulates luteal cells to secrete steroid hormones
Stage 2: Implantation to 3rd month
- By the 10th day after ovulation, hCG rescues corpus luteum
- hCG peaks in first 3 months of pregnancy
Stage 2: 4th month to term
- Steroid hormones come from the placenta to maintain the uterus
- Not controlled by hCG
- Limited only by amount of cholesterol
Estrogen production requires what?
The fetus!
Progesterone
- Conversion of uterus to secretory gland readying it for implantation
- Formation of cervical plug
- Inhibition of myometrial contraction
- Inhibition of prostaglandin synthesis from uterus
- Development of alveolus & lobule in breast
- Inhibition of lactose synthesis
Estrogen
- Massive growth of uterus, esp. of myometrium
- Development of ductile system of breasts
- Stimulates prolactin release by anterior pituitary
- Relax & soften pelvic ligaments
- Inhibits lactation
Human Placental Lactogen (HPL)
- Shifts glucose availability towards fetus
- aka. human chorionic somatomammotropin (hCS)
- Made by the placenta
- Stimulates breast development
- Activates enzymes in breasts that produce milk
- Has metabolic actions similar to GH
Where does prolactin come from?
Material anterior pituitary
Initiation of labor
- Unknown
- Likely due to both maternal & fetal signs
- Local synthesis of prostaglandins
Events contributing to parturition
- Braxton hicks contractions
- Increase in estrogen/progesterone ratio
- Local production of prostaglandins
- Increase in oxytocin receptors in myometrium, induced by increasing levels of E2
During labor
- Oxytocin pulsatility increases 3-4 times in the 1st stage of labor
- Uterine contractions start at top of uterus & push fetus toward cervix
- Cervix stretches, activates stretch receptors, stimulates hypothalamus to release oxytocin
- Oxytocin increases contractions (+ feedback)
Stage 4: Lactation
Secretory apparatus in the breast = alveoli
- Alveolar cells: site of milk synthesis
- Myoepithelial cells: smooth muscle cells
Hormones of lactation
- Estrogens stimulates ductal growth
- Progesterone, prolactin & hPL stimulate development of lobules & alveoli
- Prolactin & hPL stimulate milk enzymes & proteins (-casein)
Prolactin effects
- Inhibits GnRH secretion
- Inhibits the action of GnRH on the pituitary –> inhibiting LH & FSH release
- Antagonizes action of LH & FSH on the ovaries
What is required to maintain lactation?
Suckling
What is menopause associated w/ ?
A decline in estrogen & progesterone made by the ovaries
Stages of menopause
- Perimenopause: menstrual cycles are irregular but have not stopped
- Menopause: final menstrual period
- Postmenopause: after no periods for at least 1 year
Cause of menopause
- Related to a drop in the critical mass of eggs - “follicles”
- Decline in fertility = decline in ovarian fxn
- Average age: 51 years
- Premature menopause (earlier than 40 yo)
How does menopause occur?
- Ovarian follicle reserve declines
- Estrogen & progesterone levels decline
- Reduces negative feedback on the hypothalamic-pituitary system –> rise in FSH
- Remaining ovarian follicles are less responsive to FSH
- Menopause occurs when the residual follicles are refractory to elevated concentrations of FSH
Dx of menopause
- When FSH is > 30 mIU/ml.
- No menses for 12 months in women of typical age range
Sx of menopause
- Irregular bleeding
- Hot flash/flush –> loss of sleep, depression, irritability
- Urogenital changes
- Decline in cognitive function
- Wrinkles, weight gain, decreased libido
Urogenital changes
- Deterioration breast, uterus, vagina
- Decrease in vaginal secretions, change in pH
- Deterioration of bladder fxn
Other estrogen-deficiency changes
- Wrinkles
- Weight gain
- Tissue changes
Osteoporosis
- Reduction of bone due to lack of estrogen
- Loss of estrogen = loss of ca2+
Heart disease
- Leading cause of death among women
- Women have a 46% lifetime probability of developing CHD & a 31% probability of dying from it
- Estrogen increases HDL
- Decreases LDL cholesterol
