SIADH Flashcards Preview

Endocrinology > SIADH > Flashcards

Flashcards in SIADH Deck (66)
Loading flashcards...
1

What does SIADH/SIAD stand for?

- Syndrome of Inappropriate Secretion of Antidiuretic Hormone
OR
- Syndrome of Inappropriate Antidiuresis

2

What is osmolality?

A measure of the solute (Na, K, Cl) concentration in a unit of water.

3

What is anit-diuretic hormone (ADH)?

- Also called Arginine Vasopressin.
- Produced by the hypothalamus and stored in the posterior pituitary gland.

4

What are the 2 primary functions of ADH?

- Regulates water retention in Kidneys
- Vascular constriction

5

SIADH is a result from?

- Hyponatremia and hypo-osmolality
- Resulting from inappropriate, continued secretion or action of ADH despite normal or increased plasma volume, which results in impaired water excretion.

6

Hyponatremia is a result of what?

Hyponatremia is a result of an excess of water rather than a deficiency of sodium.

7

In general, SIADH is due to what 3 things?

1. Elevated levels of ADH
2: Water retention
3: Loss of or dilution of certain electrolytes or solutes (Na, K, Cl)

8

What is the most important effect of ADH?

Conserve water by reducing water loss through the kidneys.

9

Higher ambient temperatures causes what?

Loss of water via sweat.

10

Increased plasma osmolarity causes what?

A concentration of blood solutes.

11

What is the pathophysiology of ADH (Vasopressin)?

- Vasoconstrictor.
- Synthesized in the hypothalamus .
- Stored in the posterior pituitary.
- Endocrine negative feedback mechanism from Osmoreceptors in hypothalamus.

12

What are the kidneys response to ADH?

- ADH increases the permeability of the distal convoluted tubules in the nephrons
- This allows for water reabsorption, thus preventing water loss.

13

ADH activity dilutes what?

ADH activity dilutes blood levels of solutes.
- water reabsorption NOT solute absorption.

14

What are the CNS response to ADH?

- Dysarthria: Slurred or slow speech
- Lethargy
- Confusion
- Delirium
- Seizures
- Coma (from brain swelling)

15

Most cases of SIADH have what etiology? and what are most caused by?

- Cancer etiology
- 70% are caused by Small Cell Lung CA .

16

Where are some ADH producing tumors?

- Carcinomas (Small Cell)
- Bronchogenic
- Pancreatic
- Prostatic
- Duodenal
- Colon
- Thymoma
- Thymus gland
- Leukemia
- Lymphoma

17

What are common causes of SIADH in pulmonary disease?

- Asthma
- Pneumonia
- Tuberculosis
- Lung Abscess

18

What are the CV responses to ADH?

- ADH increases peripheral vascular resistance and thus increases arterial blood pressure.
- Becomes an important compensatory mechanism for restoring blood pressure in various forms of hypovolemic shock

19

What are the forms of hyopvolemic shock?

- Dehydration
- Bleeding
- Vomiting
- Burns
- Diuretics

20

What are common causes of SIADH in CNS disorders?

- Meningitis / Encephalitis
- CVA
- Brain Abscess
- Intracranial hemorrhage
- Cerebral aneurysm
- Subdural bleeds
- Head trauma
- Vascilitis: Lupus

21

What drugs cause SIADH?

- Antibiotics: Ciprofloxin
- SSRI’s: Fluoxetine (Prozac)
- TCAs
- Carbamazepine (Tegretol):
- Chlorpropamide: Sulphonylurea
- Cyclophosphamide: tx of Lymphoma

22

What level of sodium is indicative of hyponatremia?

<135 mEg/L

23

What are sxs of sodium <130?

- Weakness
- Weight gain
- HA
- Anorexia
- Lethargy

24

What are sxs of sodium <115?

- Mental status changes
- Seizures
- Coma

25

What are neurological sxs of SIADH?

- Irritability
- Personality changes
- HAs
- Combativeness
- Confusion
- Hallucinations
- Seizures
- Coma
- Decreased Reflexes

26

What are GI sxs of SIADH?

- Nausea
- Vomiting
- Muscle cramps

27

What are medical comorbidities of SIADH?

- CHF
- Liver failure
- Renal failure
- Pneumonia

28

Hyponatremia is recognized only secondary to the comorbidity sxs such as what?

- Dyspnea
- Jaundice
- Uremia
- Cough

29

The recognition of SIADH is entirely what? and pts may develop clinical sxs d/t what?

- Entirely incidental.
- Sxs may be d/t the cause of hyponatremia or hyponatremia itself.

30

What labs/imaging should you consider for SIADH workup?

- CBC
- CMP
- Plasma Cortisol
- CT of the head: Meningitis
- CXR: SCLC
- Radioimmunoassay of ADH