Hypothalamus and pituitary

where does the pituitary sit?

sella turcica

match terms to adenohypophysis or neurohyphysis

the median eminence, pars distalis, infundibular stem and process, pars tuberalis

Adeno: ant pituitary: pars distalis, pars tuberalis

neurohyophysis: post pituitary, median eminence, infundibular stem, infundibular process

Anterior pituitary secretion system

Posterior pituitary secretion system

1. Hypothalamus releases Releasing Hormone into capillary bed

2. Goes through portal vessel into anterior pituitary

3. Ant pituitary releases trophic hormone into systemic circulation

1. Does not use portal circulation

2. Hypo sends hormones down to the posterior pituitary via axon stalks

3. Post pituitary releases into systemic circulation

somatotrophin functions (4), released from where?

Anterior pituitary

1. Cartilage and bone growth

2. Protein metabolism: increase amino acid uptake in cells and increase protein synthesis

3. Carb metabolism: tend to increase blood glucose levels (anti-insulin effect)

4. lipid metabolism: create more free fatty acids

regulation of GH

• Growth Hormone releasing hormone (influenced by IGF-1/end result)

  • excercise, low blood glucose, low FFA (free fatty acids), high amino acids stimulate hypothalamus to produce

• feedback is positive inhibitory loop

  • IGF-1 causes release of somatrophin by hypothalamus, which is inhibitory

  • IGF-1 is negative feedback in short and long loop

where are the GH target cells? what do they produce

mainly in liver, IGF-1

disorders of GH

• pituitary dwarfism: normal proportions, small body size

  • no longer problematic in USA due to GH injections

• Adult GH deficiency: tired and weak later in life

  • only if there is damage to pituitary

• Gigantism: increase in body size, esp height

  • Presents in childhood

  • Should only grow in puberty, this disease keeps you growing

• Acromegaly: gigantism in adults

  • only certain areas of bones: hands, feet, forehead, nose, etc.

  • Andre the giant

• Aging: harder to maintain muscle mass

Prolactin function, release by?

• Breast development and milk production

  • levels go up during puberty and pregancy

• released by ant pituitary

Regulation of prolactin

• During pregnancy: progesterone and estrogen inhibit milk production

• After birth, levels go down and allow prolactin to make milk

• Suckling inhibits dopamine from hypo, which has increase effect on prolactin release

  • also slightly increase TRH release from hypo, which slightly increases prolactin release

• Prolactin negative feedback on hypothalamus

Disorder of prolactin

• hyperprolactinemia

  • if prolactin is high, other sex hormones are shut down

  • tumors or damage to stalk

  • Anorrhea: lack of menstration

  • Galactorrhea: too much milk

  • Decrease in libido: infertility and low sex drive

Oxytocin: function, release by>

• release by post pit

• Milk letdown when baby suckles (myoepithelial cells contract and delivers milk into duct)

• Uterine contraction

  • positive feedback

    • cervical dilation → oxy release → uterine contraction → dilation

  • also important to reduce blood loss at end of delivery

• Trust for other humans

Arginine vasopressin (ADH)

• Increases H2O resorption in kidney

• Osmolarity increases → increases ADH release → increases H2O resorption

• Also stimulated by angiotensin II and epinephrine

Diabetes insipidus

• if ADH is not present, a lot of urine is produced

• idiopathic is most common, but can can be caused by tumors, post-hypophysectomy, head trauma

• Analog of ADH is given as treatment

How does alcohol affect ADH?

Inhibits: more urine, = dehydration and hangover