Physiology of the breast Flashcards
What do the mammary buds form in males and females
Males: Development is suppressed by androgens, although maternal hormones cause some increase and milk secretion
Females: Duct system
What is the effect of the following hormones on breast development:
- Estrogen
- Progesterone
- Prolactin
- Oxytocin
Estrogen: Proliferation of mammary ducts
Progensterone: Development of lobules and alveoli
Prolactin: Milk production
Oxytocin: Myoepithelial cell contraction - excretion
What are the effects of estrogen on the breast during puberty
Increase in size
Increase in pigmentation of aereola
Formation of mass beneath areola: Thelarche
Which hormones are responsible for the development of true glandular acini during pregenancy
Prolactin
Human placental lactogen
Estradiol
Progesterone
Insulin
Cortisol
GH
IGF-1
EGF
What are the effects of increasing estradiol levels throughout pregnancy on other hormone levels
It acts at the hypothalamic level to increase prolactin secretion
How does progesterone antagonize the action of prolactin at its receptor
- Inhibiting upregulation of prolactin receptor
- Reducing Estrogen binding
- Competing for binding at glucocorticoid receptor
How long does it take for prolactin, estrogen and progesterone elevations to be cleared postpartum
Prolactin: 7days
Estrogen: 3-4days
Progesterone: 3-4days
How does the levels of prolactin fluctuate postpartum
1st week: levels decrease by 50%
Until 2-3months: Basal levels are 40-50ng/ml
10-20fold increase while suckling
3-6th month: Basal levels remain normal with 2 times increase with suckling
What happens to progesterone postpartum
Progesterone has less effect once lactation has begun: Number of progesterone receptors have decreased significantly
Progesterone has greater affinity for milk fat than for progesterone receptor so is cleared quickly
How can lactation be inhibited
Bromocriptine - dopamine agonist
2.5mg bid for two weeks
Breast binding, ice and avoidance of nipple stimulation will result in cessation of lactation after 1 week
What is the mechanism of male gynaecomastia
Increase estrogen levels: testicular and adrenocortical tumours, liver failure, estrogen exposure
Increase aromatase activity: liver disease, hyperthyroidism, androgen insensitivity, obesity, XXY
Decreased androgens: Klinefelters, anorchia, hypogonadism
Estrogen receptor agonist: Digoxin, phytoestrogens
What are the effects of hormones in breast cancer
35% of breast cancer in pre-menopausal estrogen-dependant: decreased estrogen levels decreased effects
