Female Endocrine😊

Lactation

  • Mammogenesis > lactogenesis > galactokinesis > galactopoiesis
Process
Meaning
Hormones / Mechanism Involved
1. Mammogenesis
Growth of breast
• Estrogen: Aids ductal growth.

• Progesterone: Promotes lobulo-alveolar growth.

2. Lactogenesis
Production of milk
• Prolactin
• Insulin
• Growth Hormone

Mnemonic: PIG Produce milk
3. Galactokinesis
Release of milk
↳ Milk ejection
↳ Let down reflex
Mechanism:
• Suckling → Stimulates hypothalamus → Oxytocin release from posterior pituitary.

Neuroendocrine reflex.

Inhibited by: anxiety, pain, depression.
4. Galactopoiesis
Maintenance of lactation
- Prolactin

Estrogen

  • â›” Milk production during pregnancy.
    • â›” Premature lactation
    • Acts by inhibiting prolactin-mediated milk synthesis.
  • Levels
    • High during pregnancy
    • Fall after delivery → Lactation begin

Oxytocin:

  • It is released from the posterior pituitary gland
  • Positive feedback mechanism
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Milk Ejection Reflex / Let-down reflex
Uterine Contraction
Trigger
Baby sucks on nipples
(activates touch receptors)
Baby head touches cervix
Action
Myoepithelial cells contract
↳ BREAST CRAMPS
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Result
Milk ejection from alveoli into ducts
↑↑ uterine contraction and cervical dilatation

Hormonal Actions

Estrogen
Target Organ
Actions
Uterus 
(Estrogen dominant)
• Increases blood flow.
• Increases contractility, increases excitability.
• Menstruation
Vagina
• Vaginal Cornification
Cervix
• Cervical mucus production
Secondary sexual characteristics
• Creates female body contour.
• Promotes fat distribution in breast & buttocks.
• DO NOT CAUSE PUBIC OR AXILLARY HAIR GROWTH
Breast
• Promotes growth.
• Aids ductal proliferation.
Bone
• Produces Osteoprotegerin (inhibitor of RANK ligand).
• ↓↓ osteoclast differentiation → ⛔ bone resorption → Protects bone
Liver
• ↓↓ plasma LDL cholesterol
CVS
• ⛔ platelet activation → ↓ Clot formation
• Promotes vasodilation by increasing NO
CNS
Neuroprotective:
• ⛔ neuronal cell death
Kidneys
• Causes salt & water retention
Progesterone
Target Organ
Actions
Uterus
Anti-estrogenic action:
• Makes uterus less active, less excitable, less contractile
Breast
• Promotes lobulo-alveolar (gland) growth
CNS
Thermogenic action:
• ↑↑ Basal Body Temperature (BBT) by 0.5-1°C during ovulation.
Respiration
• Stimulates respiration → Leads to CO2 washout → ↓↓ alveolar PCO2 levels
Kidneys
Causes Natriuresis:
• Promotes salt & water excretion
• (Only steroid hormone → cause Natriuresis)

Role of Leptin in Puberty:

  • Released from: White adipose tissue
  • Functions
    • Leptin levels rise with adipose tissue mass
      • → High leptin in obesity.
    • Sends satiety signals to the hypothalamus
      • reduce fat storage.
    • Stimulates thermogenesis.
  • Permissive Role in Puberty Onset
    • Regulates circadian rhythms of gonadotrophs.
    • Increase pulsatile GnRH secretion.
    • Zero leptin → causes infertility.
  • Mnemonic:
    • Leptin (white girl) says Kazhikkalle (anorexigenic) enikk fat kuraykkanam (↓ fat storage) → enn paranj chuudavum (thermogenisis)
    • ennale enikk periods avumbo (Puberty permissive role) nalla cherukkane kittu

PROLACTIN

Regulation:

Features
Notes
Produced by
Lactotrophs in anterior pituitary
Primary inhibitory control
Hypothalamus
Inhibitors
• Dopamine
↳ Most imp
↳ Prolactin Inhibiting Factor
• Glucocorticoids
• Thyroid Hormones
Stimulators
• Thyrotropin Releasing Hormone
• Vasoactive Intestinal Peptide (VIP)

Factors Affecting Secretion:

Factors Increasing Prolactin Secretion
Factors Decreasing Prolactin Secretion
Pregnancy & Lactation
Dopamine
Sexual Intercourse
L-Dopa (dopamine precursor)
Suckling of Nipples
Bromocriptine (dopamine agonist)
REM Sleep
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  • Mechanism of Action:
    • Prolactin Acts on Cytokine receptor
    • Activates Janus Kinase
    • Initiates the JAK-STAT Pathway.
Key Actions
MOA
Milk Production
• ↑↑ proliferation of lobulo-alveolar epithelial cells in breast
Reproductive Inhibition
(Negative Regulator)
• Inhibits GnRH → ⛔ FSH & LH
• Lactational amenorrhea in ♀
• Loss of libido & ↓ spermatogenesis in ♂

Applied Aspect: Pituitary Stalk Effect

  • Lesion at the pituitary stalk 
    • Disconnects hypothalamus from pituitary
  • Consequence:
    • Significantly ↑ Prolactin 
      • d/t Loss of inhibitory dopamine
    • ↓ All other pituitary hormonesÂ