LECTURE 54 - posterior pituitary hormones

Question 2

List the functions of GH

Answer 2

• Required during childhood and adolescence for attainment of normal adult size
• Anabolic effects in muscle
  Increases lean body mass
• Catabolic effects in lipid cells
  Reduced central adiposity
• Reductions in insulin sensitivity
  (compensated by the insulin activity of IGF-1)

Question 3

List the effects of GH deficiency

Answer 3

• Failure to reach the predicted adult height
• Disproportionately increased body fat
• Decreased muscle mass

Question 4

List the clinical used for GH supplementation

Answer 4

• Treatment of GH deficiency
• Treatment of pediatric patients with short stature without GH deficiency (prader-willi syndrome, turner syndrome)
• Performance enhancer in athletics (banned by IOC)

Question 5

Describe the use of GH supplementation as a treatment for GH deficiency

Answer 5

can treat:
- Congenital deficiency– genetic mutations
- Acquired deficiency– damage to the pituitary or hypothalamus by a tumor, infection, surgery, or radiation therapy
- Short stature and adiposity in childhood
- Hypoglycemia due to unopposed action of insulin

Question 6

Describe the uses of GH antagonists

Answer 6

treating the effects of GH-secreting pituitary adenomas

effects:
- acromegaly
- gigantism (rare)

Question 7

List GH antagonists

Answer 7

Somatostatin analogs:
Octreotide
Lanreotide

GH receptor antagonist:
Pegvisomant

Question 8

List the functions of IGF-1

Answer 8

• Increase in production of IGF-1 in ver, bone, cartilage, and muscle mediates GH
• Anabolic effects in muscle → Increases lean body mass
• Catabolic effects in lipid cells → Reduces central adiposity
• Reduction in insulin sensitivity
  (compensated by the insulin activity of IGF-1)

Question 9

Name the recombinant form of human IGF-1

Answer 9

mecasermin (rhIGF-1)

used in tx of severe IGF-1 deficiency

Question 10

Describe vasopressin

Answer 10

Antidiuretic hormone (ADH), Arginine vasopressin (AVP)

Released by the posterior pituitary in response to:
Rising plasma tonicity
Falling blood volume

Question 11

List the physiological functions of vasopressin

Answer 11

• Increases reabsorption of water from tubular filtrate by increasing water permeability in the cells in renal collecting tubules (antidiuretic activity)
  – Reduction in urine volume
  – Increase in blood volume
• Constricts blood vessels (vasopressor activity)
  – Raises BP
• Increases the levels of Von Willebrand factor & coagulation factor VII

Question 12

Describe the V-1 receptor

Answer 12

• GPCR that increases cytosolic Ca2+ levels upon activation
• Found of vascular smooth muscle cells
• Mediates vasoconstriction

Question 13

Describe the V-2 receptor

Answer 13

• GPCR that increases cAMP levels upon activation
• Found on renal tubule cells
• Increases number of aquaporins on the cellular membrane → increases water permeability → water reabsorption

Question 14

Explain the receptor specificity of desmopressin

Answer 14

desmopressin is a long-acting synthetic analog of vasopressin

– has minimal V-1 activity –
(4000x’s higher antidiuretic-to-vasopressor activity vs. vasopressin)

Question 15

List the clinical used of vasopressin

Answer 15

Pituitary diabetes insipidus
– Vasopressin deficiency
– symptoms:
Polyuria
Polydipsia
Hypernatremia

Nocturnal enuresis - bed wetting

Coagulopathy in hemophilia A & von Wilderbrand’s disease

Question 16

List the adverse effects of vasopressin

Answer 16

• water intoxication
• vasopressin should be used with extreme caution in persons with CV diseases
• abdominal cramping
• allergic reaction (rare)

Question 17

List the symptoms of water intoxication

Answer 17

Hyponatremia
Drowsiness, listlessness, headache
Fluid intake needs to be limited

Question 18

Describe how hyponatremia (an adverse effect of vasopressin) can be treated

Answer 18

Vasopressin antagonists:
Conivaptan (IV)
Tolvaptan (oral)

Question 19

List the clinical used of oxytocin

Answer 19

Uterine contraction in L&D:
– Induction & stimulation of labor (IV via infusion pump)
– Control of uterine hemorrhage after delivery (IV)

Milk ejection in lactating women:
– Enhancement of milk ejection (nasal spray)

Question 20

List the adverse effects of oxytocin

Answer 20

Excessive stimulation of uterine contraction before delivery:
– Fetal distress
– Placental abruption
– Uterine rupture
– Trauma to birth canal

Activation of vasopressin receptors by overdose of oxytocin:
– Excessive fluid retention
– Water intoxication
– Hyponatremia

CONTRAINDICATIONS:
– Fetal distress
– Abnormal fetal presentation
– Cephalopelvic disproportion

Question 21

List GH drugs

Answer 21

somatropin:
Genotropin®
Humatrope®

Question 22

List IGF-1 drugs

Answer 22

mecasermin:
Increlex®
Iplex®

Question 23

List somatostatin analogs

Answer 23

Octreotide (Bynfezia®, Sandostatin®)
Lanreotide (Somatuline®)

Question 24

List GH antagonists

Answer 24

Pegvisomant (Somavert®)

Question 25

List vasopressin agonists

Answer 25

Vasopressin (Vasostrict®) Desmopressin (DDAVP®, Stimate®)

Question 26

List vasopressin antagonists

Answer 26

Conivaptan (Vaprisol®) Tolvaptan (Jynarque®, Samsca®)

Question 27

What is the brand name for oxytocin?

Answer 27

Pitocin®