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Endocrinology > Week 3 - Posterior Pituitary > Flashcards

Week 3 - Posterior Pituitary Flashcards

1
Q

Which 2 hormones are secreted by the posterior pituitary?

A
  1. Oxytocin

2. Antidiuretic hormone (ADH)

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2
Q

What are 2 functions of ADH?

A
  1. Maintenance of plasma osmolality

2. Actions on the kidney

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3
Q

What are 2 disorders of the posterior pituitary?

A
  1. Syndrome of inappropriate antidiuretic hormone (SIADH)

2. Diabetes Insipidus

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4
Q

T/F: Posterior pituitary is not a gland but only the distal axon terminals of the hypothalamic magnocellular neurons

A

True

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5
Q

Hormones originate in the ____________ nucleus of the hypothalamus, travel down the axons of neurons to the posterior pituitary, where they enter general circulation

A

paraventricular

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6
Q

Oxytocin is primarily from the posterior pituitary, which 6 other glands also secrete oxytocin ?

A
  1. Corpus luteum (placenta)
  2. Leydig cells (male testes)
  3. Retina
  4. Adrenal Medulla
  5. Thymus
  6. Pancreas
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7
Q

What are the 2 major functions of oxytocin?

A
  1. Milk secretion during lactation (Letdown reflex) - stimulates contraction of smooth muscle in the breast
  2. Contraction of the uterine smooth muscle during labor - also involved in cervical dilation
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8
Q

What are 2 sexual functions of oxytocin?

A
  1. Stimulate pair-bonding/maternal behaviors

2. Released during orgasm: possibly associated with sexual arousal

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9
Q

Anti-stress effects of oxytocin produce which 5 responses?

A
  1. Lowers BP
  2. Lowers cortisol levels
  3. Increase tolerance to pain
  4. Reduces anxiety
  5. Anti-depressant
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10
Q

Low levels of oxytocin and oxytocin receptor genes (OXTR) have been found associated with which condition?

A

Autism

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11
Q

Oxytocin is available as an injection called ________

A

Pitocin

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12
Q

What is the other term for ADH?

A

Vasopressin (Arginine vasopressin - AVP)

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13
Q

Which 2 signals stimulate ADH release?

A
  1. Increase in plasma osmolality

2. Decrease in plasma volume

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14
Q

An increase in plasma osmolality is detected by _______ in the hypothalamus and triggers _______.

A

osmoreceptors; thirst (as does hypotension and hypovolemia)

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15
Q

T/F: Nausea triggers ADH release

A

True

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16
Q

A decrease in plasma volume is detected by ________ in the chest, carotid sinus, aortic arch, and pulmonary venous system.

A

Baroreceptors

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17
Q

T/F: ADH secretion is more greatly influenced by changes in plasma volume than by changes in osmolality

A

FALSE! ADH secretion is LESS influenced by changes in plasma volume than by changes in osmolality

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18
Q

What is the term for a measure of the body’s electrolyte-water balance?

A

Plasma osmolality

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19
Q

Which 6 nutrients mostly determine plasma osmolality?

A
  1. Na (most important osmole)
  2. Cl
  3. bicarbonate
  4. proteins
  5. glucose
  6. urea
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20
Q

When ADH secretion is increased it triggers which response to water, which does what to plasma osmolality? What happens to urine and thirst?

A

Water is retained; DECREASING plasma osmolality;
Urine is more concentrated
Thirst is stimulated

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21
Q

Pressure and volume of blood are mediated by changes in ___________ balance Determined mostly by which 3 things?

A 
Sodium (Na+)
1. Renin
2. Angiotensin
3. Aldosterone 
(all secreted by the kidneys/adrenals)
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22
Q

What is the main action of ADH?

A

Decreases water excretion in the kidneys

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23
Q

ADH causes water resorption in _________ of the kidneys via _____________

A

Collecting ducts

via aquaporin-2

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24
Q

Ethanol and caffeine _______ ADH secretion - this results in what response to fluid

A

reduces; MORE fluid excreted

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25
Q

ADH does what to BP? How?

A

Raises BP; constricts peripheral capillaries

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26
Q

What are the 4 forms of diabetes insipidus?

A
  1. Central
  2. Nephrogenic
  3. Dipsogenic
  4. Gestational
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27
Q

Which form of DI is a true deficiency of ADH?

A

Central DI

28
Q

Which form of DI is kidney or nephron dysfunction which causes an insensitivity of kidneys to ADH?

A

Nephrogenic DI

29
Q

Which form of DI is from excessive intake of fluids and maybe due to damage of hypothalamic thirst mechanism or mental illness?

A

Dipsogenic DI

30
Q

Which form of DI occurs during pregnancy and post partum periods? The placenta produces vasopressinase which breaks down ADH and is associated with acute fatty liver and pre-eclampsia.

A

Gestational DI

31
Q

Excess ADH leads to which 4 things?

A
  1. Reduced urination
  2. Concentrated urine
  3. Edema & hypervolumia
  4. Dilutional hyponatremia
32
Q

Lack of ADH activity leads to which 4 things?

A
  1. Excessive urination
  2. Dilute urine
  3. Excessive thirst
  4. Dehydration
33
Q

What are 4 treatment options for SIADH?

A
  1. Water restriction
  2. Diuretic
  3. Salt Administration
  4. Various medications
34
Q

What are 3 treatment options for DI?

A
  1. Synthetic ADH (desmopressin)
  2. Remove cause
  3. Various medications
35
Q

Hyponatremia is classified as ____ mEq/L

A

<135mEq/L

36
Q

Hyponatremia may cause a shift of fluid from the vascular space to the intracellular space. What is the most important consequence?

A

cerebral edema

37
Q

Which condition causes acute cerebral edema, nausea, vomiting, headache and if worsens can lead to seizure, coma, respiratory arrest and has a 50% mortality

A

Acute hyponatremia (develops <24 hours)

38
Q

Which condition causes lethargy, confusion, muscle cramps, neurologic impairment and has a 10% mortality (associated with underlying condition)?

A

Chronic hyponatremia (develops > 48 hours)

39
Q

Which part of the body is least tolerant of hyponatremia? What is a treatment for seizures related to this condition?

A

The skull

Tx with 100ml bolus of 3% solution of hypertonic saline IV

40
Q

What are 3 types of hyponatremia?

A
  1. Hypertonic
  2. Isotonic
  3. Hypotonic
41
Q

Which type of hyponatremia is caused by resorption of water caused by glucose or mannitol?

A

Hypertonic

42
Q

Which type of hyponatremia is considered “pseudohyponatremia” and is caused by measurement error or high triglycerides or proteins?

A

Isotonic

43
Q

Which type of hyponatremia is considered “true hyponatremia”, is the most common type, and is associated with low plasma osmolality?

A

Hypotonic

44
Q

What are the 3 types of hypotonic hyponatremia?

A
  1. Hypervolemic
  2. Euvolemic
  3. Hypovolemic
45
Q

Hypervolemic hyponatremia is ________TBW and ___________ total body Na

A

Increased; increased

46
Q

What are 5 causes of hypervolemic hyponatremia?

A
  1. CHF
  2. Kidney Dz
  3. Conn syndrome
  4. Cirrhosis
  5. Intake of excessive salt water
47
Q

What are 3 treatments for hypervolemic hyponatremia?

A
  1. Fluid restriction
  2. Sometimes a diuretic
  3. Correct underlying cause
48
Q

Euvolemic hyponatremia is ________TBW with ___________ ECF and total body Na

A

Increased; near normal

49
Q

What are 8 causes of euvolemic hyponatremia?

A
  1. Pharmaceuticals (diuretics, barbiturates, etc.)
  2. Addison disease
  3. Hypothyroidism
  4. SIADH
  5. Primary polydipsia
  6. Pain
  7. Post-op state
  8. “Beer potomania”
50
Q

What are 3 treatment options for euvolemic hyponatremia?

A
  1. Fluid restriction (<1 liter/24 hours)
  2. Possibly vaptans
  3. Correct underlying cause
51
Q

Hypovolemic hyponatremia is ________TBW/ECF and Na with ___________ total body Na

A

Decreased; relatively greater decrease

52
Q

What are 5 causes of hypovolemic hyponatremia?

A
  1. Low intake of water and low sodium intake (m/c in elderly)
  2. GI losses (diarrhea/vomit)
  3. Skin losses (sweating, burns)
  4. Renal (glycosuria, kidney dz)
  5. “Appropriate” secretion of ADH (seen in severe GI illness, marathon runners, and heavy exercisers)
53
Q

What is the treatment for hypovolemic hyponatremia? What is a risk of this treatment?

A

IV saline 0.9% (not to exceed 10mEq/24 hours)

Risk of osmotic demyelination syndrome

54
Q

Correcting hyponatremia too rapidly may result in ______ ______ _______ with permanent neurological deficits

A

Central pontine myelinolysis (CPM)

55
Q

What is first-line treatment of SIADH?

A

Restrict fluid intake (1-1.5 liters/day)

56
Q

What are 2 second-line treatments of SIADH?

A
  1. Increase solute intake with 0.25g/kg per day of urea
    - OR-
  2. Combo of low-dose loop diuretics and oral sodium chloride
57
Q

T/F: Use of lithium, demeclocycline, or vasopressin receptor antagonists are recommended treatment for SIADH

A

FALSE! They are NOT recommended

58
Q

T/F: Symptoms of DI are similar to those of untreated DM, except that urine does not contain glucose

A

True

59
Q

What are 3 major clinical features of DI?

A
  1. Polyuria
  2. Polydipsia
  3. Low urine osmolality
60
Q

What are 4 ways to diagnose DI?

A
  1. Head MRI (r/o pituitary/hypothalamic lesion)
  2. Measure ADH levels
  3. Water deprivation testing
  4. Desmopression stimulation test
61
Q

What are 5 etiologies of Central DI?

A
  1. Pituitary tumor
  2. Autoimmune
  3. Surgery
  4. Ischemic encephalopathy
  5. Idiopathic
62
Q

What are 2 etiologies of Nephrogenic DI?

A
  1. Hereditary (ADH receptor mutation)

2. Secondary to hypercalcemia, lithium, demeclocycline (ADH antagonist)

63
Q

What is the difference in ADH levels between Central and Nephrognic DI?

A

Central DI: Decreased ADH

Nephrogenic DI: Normal ADH levels

64
Q

What is treatment for Central DI?

A

Intranasal desmopressin acetate

Carbamezepine

65
Q

What is treatment for Nephrogenic DI?

A

HCTZ, Indomethacin, Amiloride

Endocrinology (13 decks)

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