Flashcards in Posterior Pituitary- Hypo/hypernatremia Deck (23)
urinating too much
What is Central Diabetes Insipidus
Lack of ADH secretion due to posterior pituitary pathology.
Can be a tumor, head trauma, granulomatous disease involving the hypothalamic pituitary area, CNS infection, cerebral vascular disorder
The clinical features of central diabete insipidus are
- Polyuria (pee too much) and polydypsia (excessive thirst)
- Low urine osmolality and specific gravity
- Nocturia is usually present and can lead to chronic tiredness and poor performance at work or school.
Water deprivation will do what to urine osmolality with central diabetes insipidus
NOTHING> urine osmolality will still be low
Treatment of Central Diabetes insipidus
Nephrogenic Diabetes Insipidus is what
Impaired renal response to ADH
No response to Desmopressin in
Excessive ADH secretion
ADH and Oxytocin have what structure
Stimuli that influence AVP Release?
1) Osmoregulation: primary regulator, Increases in osmolarity cause osmoreceptors in the hypothalamus to shrink. This alters the electric activity of the neurons and increases AVP release. Osmolarity maintained within a very narrow range, 280-296
2) Volume regulation: decreases in plasma volume sensed by stretched receptors in the left atrium lead to increased vasopressin release due to decreased inhibitor pulses from the left atrium to the hypothalamus
3) Baroreceptor Activation in response to hypotension: increased AVP
4) Neural regulation
6) Pharmacologic influences
7) Water Deprivation
ADH and Cortisol have opposite effects. Explain
Cortisol raises the osmotic threshold for AVP secretion
Which aquaporin is the major mediator of vasopressin action in the kidney and where is it located?
Conditions associated with water retention: CHF, Pregnancy, SIADH are often associated with what>
increased AQP2 expression
urine volume greater than 2.5 liters in 24 hours
Plasma ADH is low and doesn't increase with addition of hypertonic saline
Central DI pts respond to AVP administration
Nephrogenic DI pts do not
What would plasma osmolality and urine osmolality be like in pts who have a habitual habit of drinking too much water
Both would be low
Water deprivation test would do what to the urine osmolality of someone with polydipsia
Cause it to increase. There is nothing wrong with their ADH secretion or sensitivity to ADH.
Causes of SIADH
Malignant tumors with autonomous AVP release (lung cancer- small cell)
Non-malignant pulmonary disease
CNS disorders like meningitis
What happens to sodium levels in SIADH
They decrease, sodium secretion enhanced. Most likely because of suppression of Aldosterone release due to high plasma volume.
Suspect SIADH when a pt has
hyponatremia with a urinary osmolality that is hypertonic relative to the plasma
What are the primary stimuli for oxytocin release
mechanical distension of the reprod tract and suckling at the nipples