Structure of Mammary Gland
Milk Synthesis and Secretion
Preparation for Lactation during Pregnancy
- Mammogenic hormones (promote cell proliferation)
- Lobulo-alveolar growth
- Estrogen
- Growth hormone
- Cortisol
- Prolactin
- Ductal growth
- Estrogen
- Growth hormone
- Cortisol
- Lobulo-alveolar growth
Lactogenic Hormones
Promote initiation of milk production by alveolar cells
- Prolactin (member of somatomammotropin family)
- Human chorionic somatomammotropin (aka human placental lactogen)
- Cortisol
- Insulin
- Thyroid hormones
Hormones that inhibit milk production
Cause women not to lactate during pregnancy
- Estrogen
- Progesterone
- Removal of inhibition with parturition permits lactation
- Combination OCPs may interfere with lactation
- Taking BC with estrogen can inhibit lactation
Placenta delivery –> ß estrogen –> milk secretion
Maintenance of Lactation
Galactokinetic hormones (promote contraction of myoepithelial cells; milk ejection)
- Oxytocin
Galactopoietic hormones (maintain milk production after it has been established)
- Prolactin
- Other metabolic hormones (including growth hormone)
*rBST; recombinant bovine somatotropin (rBGH; recombinant bovine growth hormone)à increases milk yield of lactating cows
Regulation milk secretion and ejection
Lactation Stimuli and Hormone Release
- Lactation can become condition to stimuli other than suckling
- PRL is not secreted in response to anticipatory stimuli
- Oxytocin release can be conditioned to other stimuli (such as a bab y crying)
- Longer nursing session will produce more milk, PRL doesn’t get released until baby starts suckling; PRL doesn’t get release until baby starts suckling, milk at end of session has more caloric content
Milk Composition
- Human Colostrum (first ~5 days post partum)
- Less fat, low carbs, high protein, lots of antibodies, less volume
- Human Milk
- High fate, high carbs, low protein, fat-soluble vitamins, antibodies
- Cow’s milk
- 3X more protein (mostly due to casein), high electrolyte content
*Important to try to breast feed in first week because most antibodies are passed
Milk and Formula Comparison (per 100mL)
*Formula has more protein, less fat, more electrolytes and no cells
Breastfeeding Recommendations
- American Academy of Pediatrics recommends that babies be exclusively breastfed for about first 6 months of life
- Baby needs no addition foods (except Vitamin D) or fluids unless medically indicated
- Babies should continue to breastfeed for a year or for as long as is mutually desired by mother and baby
Lactational Amenorrhea
- Lactational amenorrhea (lack of menstrual cycles) and anovulation (lack of ovulatory cycles) affords some level of contraception
- Duration of lactational amenorrhea is highly variable (depends on frequency and duration of lactation)
- Proposed roles doe kisspeptin and prolactin
- Suckling inhibits GnRH secretion
- Decline in GnRH reduces LH & FSH secretion to inhibit ovarian cycle
Kisspeptin Review
Role of Kisspeptin in Lactational Amenorrhea
- Lactation suppresses KiSS-1 mRNA expression in ARC
- Kiss-54 injection stimulates pulsatile LH sectretion
- GnRH neurons are capable of responding to Kisspeptin, suggesting inhibition of Kisspeptin expression due to lactation is involved in suppression in LH secretion
Role of Prolactin in Lactational Amenorrhea
Part 1
- Hyperprolactinemia suppresses gonadotropins secretion and is major cause of amenorrhea in humans
- Mechanism is unresolved but may involve combined suppressive effects of dopamine and prolactin on onadotropin response to GnRH
Role of Prolactin in Lactational Amenorrhea
Part 2
- Gonadotrophs have receptors to DA and PRL
- GnRH stimulates gonadotropins (LH & FSH) a-subunit mRNA expression in aT3-1 cells
- Bromocriptine (Br; a DA agonist) and PRL, alone or in combination, suppress GnRH-induced gonadotropin a-subunit mRNA expression
Breast Pumps
- Breast pumps extract milk from breast by creating vacuum around nipple that pulls air into breast-shield, and applies and releases suction in a cyclic manner
Why pump?
- Return to work
- Tracel or any other separation from baby
- Allow father or other caretake to bottle feed
- Collect milk to feed premature baby
- Boost milk supply
Milk Banks
Donor Milk Banking- Collection, screening, processing, and distribution of human milk from volunteer breastfeeding mothers
- Initially used nearly exclusively for premature infants
- Currently used for older infants and children with major nutritional or immunological problems
- Cost: ~ $3 per ounce
Informal Milk Sharing- Sharing expressed milk with friend, neighbor or acquaintance
- Potential transmission of HIV, hepatitis, and other viri or bacteria through human milk
Breast implants
- Saline or silicone implant is placed behind natural breast tissue to increase breast size
- Women with breast implants product less milk than women without them
- Ability to breastfeed depends on type of surgery; incision locations include
- Periareolar (“smile incision around areola; most popular method)
- Transaxillary (through armpit)
- Transumbilical (through belly button)
- Inframammary fold (underneath the breast)
Problems with Breastfeeding with Breast Implants
- Periareolar incisions mat cut or damage nerves or duct system, introducing greater risk for breastfeeding problems
- Implant may exert pressure on glandular tissue causing pain, atrophy and/or necrosis and physically blocking ducts thus reducing milk production
