Lactation

Question 1

Structure of Mammary Gland

Question 2

Milk Synthesis and Secretion

Question 3

Preparation for Lactation during Pregnancy

Answer 3

• Mammogenic hormones (promote cell proliferation)
  
  • Lobulo-alveolar growth
    
    • Estrogen
    • Growth hormone
    • Cortisol
    • Prolactin
  • Ductal growth
    
    • Estrogen
    • Growth hormone
    • Cortisol

Question 4

Lactogenic Hormones

Answer 4

Promote initiation of milk production by alveolar cells

• Prolactin (member of somatomammotropin family)
• Human chorionic somatomammotropin (aka human placental lactogen)
• Cortisol
• Insulin
• Thyroid hormones

Question 5

Hormones that inhibit milk production

Answer 5

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

Question 6

Maintenance of Lactation

Answer 6

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

Question 7

Regulation milk secretion and ejection

Question 8

Lactation Stimuli and Hormone Release

Answer 8

• 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

Question 9

Milk Composition

Answer 9

• 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

Question 10

Milk and Formula Comparison (per 100mL)

Answer 10

*Formula has more protein, less fat, more electrolytes and no cells

Question 11

Breastfeeding Recommendations

Answer 11

• 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

Question 12

Lactational Amenorrhea

Answer 12

• 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

Question 13

Kisspeptin Review

Question 14

Role of Kisspeptin in Lactational Amenorrhea

Answer 14

• 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

Question 15

Role of Prolactin in Lactational Amenorrhea

Part 1

Answer 15

• 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

Question 16

Role of Prolactin in Lactational Amenorrhea

Part 2

Answer 16

• 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

Question 17

Breast Pumps

Answer 17

• 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?

1. Return to work
2. Tracel or any other separation from baby
3. Allow father or other caretake to bottle feed
4. Collect milk to feed premature baby
5. Boost milk supply

Question 18

Milk Banks

Answer 18

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

Question 19

Breast implants

Answer 19

• 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)

Question 20

Problems with Breastfeeding with Breast Implants

Answer 20

• 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