Flashcards in Biochemistry (Weeks 4 + 5) Deck (27):
What does mineralocorticoid activity refer to?
In exchange for K+ and/or H+
What steroids have mineralocorticoid activity?
Aldosterone (main one)
What does excess mineralocorticoid activity result in?
What does too little mineralocorticoid activity result in?
Na+ loss -> Water loss
What does ADH cause?
Water reabsorption -> Antidiuresis
What can cause hyponatraemia?
- Decreased secretion -> SIADH
- Increased intake -> Compulsive water drinking
Too little Na+:
- Increased Na+ loss
> Gut/Skin loss
- Decreased Na+ intake (rare)
What can cause hypernatraemia?
Too little water:
- Increased water loss -> Diabetes Insipidus
- Decreased water intake - Young/Eldery
Too much Na+:
> Medications given as IV Na+
> Ocean near-drowning
> Infants given high-salt feeds
Put the following steps in order for the development of Addison's disease:
- Decreased steroid secretion
- Na+ and water loss from ECF
- Clinical dehydration
- Adrenal insufficiency
- Decreased Na+ retention
- Decreased mineralocorticoid activity
- Decreased ECF volume
1. Adrenal insufficiency
2. Decreased steroid secretion
3. Decreased mineralocorticoid activity
4. Decreased Na+ retention
5. Na+ and water loss from ECF
6. Decreased ECF volume
7. Clinical dehydration
Which of the following is not a feature of Addison's:
- Weight gain
- Actually causes weight loss
What causes hyperpigmentation in Addison's disease?
- ACTH contains melanocyte-stimulating hormone
- ACTH degraded by proteases
- MSH exposed
- Excess pigment
How will hyperkalaemia present as on an ECG?
What are U-Waves (ECG) seen in?
What are some non-osmotic stimuli for ADH release?
What does the 'inappropriate' mean in SIADH?
Inappropriate for the osmolal state
Why can the clinical volume status be unremarkable in SIADH?
The retained water is often distributed across all body compartments
What is the pathogenesis of central diabetes insipidus?
1. Pituitary/Pituitary stalk disruption
2. No ADH secretion
3. Decreased water reabsorption
4. Loss of pure water in urine
What effect does DI have on Na+ levels?
How is diabetes insipidus treated?
Exogenous ADH -> Desmopressin
What are signs and symptoms of diabetes insipidus?
Head injury (RTA)
High urine output
Fluid replacement high -> Slow fall in [NA+]
What is the volume status of hypovolaemia?
Hypovolaemia + Hyponatraemia = Decreased Na+
Is hypo- or hypernatraemia serious?
If very low ( YES
If very high (>155mmol/L) -> YES
What symptoms can be seen in hypo- or hypernatraemia?
What is pseudohyponatraemia?
When there are excess proteins and lipoproteins in a serum sample:
- [Na+] in serum water is the same
- [Na+] in total serum appears reduced
How can a patient's volume status indicate the cause of hyponatraemia?
If dry -> Too little Na+
If not dry -> Too much water
If a patient is dry (ie too little Na+) what can be causing it?
Decreased intake (rare)
- Gut, skin or kidney?
> Gut and skin loss is obvious
If there is suspected Addison's what should be done?
If patient unwell:
- Give Na+ replacement