-
Zona glomerulosa (control by RAAS)
Secretes aldosterone
-
Zona Fasciculata (control by ACTH, hypothalamic CRH)
Secretes cortisol, sex hormones
-
Zona Reticularis (control by ACTH, hypothalamic CRH)
Secretes sex hormones
-
Medulla (regulated by preganglionic sympathetics)
Secretes catecholamines from chromaffin cells (neural crest origin)
-
Posterior Pituitary (neurohypophesis) - neuroectodermal origin
Secretes ADH and Oxytocin, carried by neurophysins
-
Anterior Pituitary (adenohypophesis) - derived from Rathke's Pouch (mesodermal?)
- "Flat Pig"
- *FSH
- *LH
- ACTH
- *TTSH
- Prolactin
- GH
- *share a-subunit (also hCG)
-
Hormones that share same a-subunit
FSH, LH, TSH, hCG
-
Endocrine pancreas cell types
- a = glucagon (periphery)
- B = insulin (central)
- delta = somatostatin (interspersed)
-
Insulin: production
B cell response to ATP from glucost metabolism
Increased ATP -> closes K+ channel -> depolarizes cell -> increased of Ca2+ -> exocytosis of insulin
-
Insulin: labs
Serum C-peptide not present with exogenous intake
-
-
GLUT-2 (bidirectional)
- Glucose transport in:
- B islet cells
- Liver
- Kidney
- Small intestine
-
GLUT-4 (insulin-responsive)
Glucose transport in: adipose tissue, skeletal muscle
-
Insulin: actions
- Increase glucose transport
- Increase glycogen synthesis and storage
- Increase TG synthesis and storage
- Increase Na+ retention
- increase protein synthesis
- Increase cellular uptake of K+ and amino acids
-
TRH stimulates release of:
TSH, prolactin release stimulated by:
-
Dopamine inhibits release of:
Prolactin release inhibited by:
-
CRH stimulates release of:
ACTH release stimulated by:
-
GHRH stimulates release of:
GH release stimulated by:
-
Somatostatin inhibits release of:
GH, TSH release inhibited by:
-
GnRH stimulates release of:
FSH, LH release stimulated by
-
Prolactin inhibits release of:
GnRH release inhibited by
-
Prolactin Regulation
Secretion from anterior pituitary inhibited by dopamine from hypothalamus
-
Prolactin self-regulation
Inhibits own secretion by increasing dopamine synthesis / secretion
-
Prolactin: function
- Stimulates milk production in breast
- Inhibits GNRH, thus:
- Inhibits ovulation (in females)
- Inhibits spermatogenesis (males)
-
Bromocriptine
- Dopamine agonist inhibiting prolactin secretion
- Treats prolactinoma
-
Dopamine antagonists (antipsychotics) and estrogens (OCPs, pregnancy)
Medications that stimulate prolactin secretion
-
17a-hydroxylase deficiency: products
- Decrease sex hormones
- Decreased cortisol
- Increased mineralocorticoids
-
17a-hydroxylase deficiency: Symptoms
- HYPERtension (increased mineralcorticoids) -> hypokalemia
- XY: decreased DHT -> pseudohermaphroditism
- XX: externally phenotypic female w/ normal internal sex organs (no secondary sex characteristics)
-
21-hydroxylase deficiency: products
- Decreased cortisol (increased ACTH)
- Decreased MC
- Increased sex hormones
-
21-hydroxylase deficiency: symptoms
- Most common form
- HYPOtension (decreased mineralcorticoids)
- Masculinization
- Female pseudohermaphroditism
- Hyperkalemia
- Increased plasma renin, volume depletion
- Salt wasting
-
11B-hydroxylase deficiency
- Decreased cortisol
- Decreased aldosterone / corticosterone
- Increased sex hormones
- Sx: masculinization, HYPERtesnsion (increased 11-deoxycortocosterone - acts like aldosterone)
-
Cortisol: function
- BBIIG
- Blood pressure (upregulates a1 receptors - works with epinephrine)
- Bone formation (decreased)
- antiInflammatory
- Immune function (decreased)
- Gluconeogensis, lipolysis, proteolysis
-
Cortisol: Regulation
- CRH -> ACTH
- (cortisol feedsback on CRH, ACTH, cortisol secretion)
-
Parathyroid: origin
- 3rd pharyngeal pouch: Inferior parathyroid / Thymus
- 4th pharyngeal pouch: Superior parathyroid
-
PTH action on bone
Stimulates osteoblasts -> increases production of M-CSF / RANK-L
-
PTH regulation
- Decreased Ca2+ INCREASES secretion
- Decreased Mg2+ DECREASES secretion
-
Vitamin D: Function
- increase absorption of dietary Ca/P
- Increase resorption of Ca2+ and PO4
-
Regulation of Vitamin D
- Increased production:
- increased PTH
- Decreased Ca2+
- Decreased phosphate
- Decreased production:
- Vitamin D
-
Calcitonin: source
Parafollicular cells (C cells) of thyroid (neural crest origin?)
-
Calcitonin: function
Decreases bone resorption of calcium
-
Calcitonin: regulation
Increased serum Ca2+ causes secretion
-
cAMP signaling pathways
- FLAT CHAMP
- FSH, LH, ACTH, TSH, CRH, hCG, ADH (V2), MSH, PTH, calcitonin, GHRH, glucagon
-
cGMP
- vasodilators
- ANP, NO (EDRF)
-
IP3
- GOAT
- GnRH, Oxytocin, ADH (V1) TRH
-
Cytosolic Steroid Receptors
- VET CAP
- Vit D, Estrogen, Testosterone, Cortisol, Aldosterone, Progesterone
-
Nuclear Steroid Receptors
T3 / T4 signaling pathway
-
Intrinsic tyrosine kinase (MAP kinase) pathway
Insulin, IFG-1, FGF, PDGF (growth factors)
-
Receptor-associated tyrosine kinase pathway (JAK/STAT)
GH, prolactin, IL-2
-
T3 functions
- Brain maturation
- Bone growth
- B-adrenergic effects
- BMR increased
-
Thyroxine-binding globulin
- Binds most T3/T4
- Decreased in hepatic failure
- increased in pregnancy / OCP use (estrogen increases TBG)
-
T4 vs T3
- T4 is major product; converted to T3 by peripheral tissue
- T3 has greater affinity
-
T3/T4 synthesis
- 1. Thyroglobulin (TG) made in follicular cell, pumped into lumen
- 2. Iodine pumped into, oxidized and organified (peroxidase) -> I2 in lumen
- 3. MIT and DIT (TG + I2) coupled to T3/T4 (peroxidase)
- 4. Proteolyzed in follicular cell, free T3/T4 spit out on basolateral side into blood
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