SIADH/hypogonad/aldosteronism Flashcards
Dorwart Chalmers Formula -
Serum Osmolality = (1.86(Na)) + (Glucose/18) + (Bun/2.8) + 9
Normal Serum Osmolality ranges from approximately
275mOsm/kg water - 295mOsm/kg water
Smithline and Gardner -
Serum osmolality = 2(Na) + glucose/18 + BUN/2.8
The Normal Response to Water Deprivation
The Normal Response to Drinking Water
Effects of ADH (3)
Increase H20 permeability in late distal tubule Collecting Duct
Increase activity of Na K 2CL transporter enhancing counter current multiplication.
Increase urea permeability in inner medullary collecting ducts
Regulation of ADH
Normal? ADH levels are almost entirely controlled by plasma osmolarity
Only a volume change of 10% or greater causes significant shifts in ADH levels
Shock (Severe Volume loss) triggers ADH secretion to maintain volume
Syndrome of inappropriate ADH
serum vs urine
serum in hypOnatremic
urine is hypertonic.
water is being retained in blood despite hydration.
beerporomania
general
beer doesnt have Na so it dilutes blood
low osmalality urine and blood,
don’t break the seal!
SIADH
general
ADH is secreted independently of osmoreceptors
Produces Hyperosmotic urine, Hypoosmotic Plasma, and Abnormally High levels of ADH
SIADH
etiology
ADH is secreted from areas that don’t respond to the feedback mechanism. Lung Tumors, Head Injuries (neuro is important exam) , Some Drugs can cause this.
(typical and atypical psychotic meds)
SIADH
Tx
- Treat the Hyponatremia first, the root cause second. Do NOT correct the sodium rapidly.- can cause locked in syndrome.
- First Line treatment - Fluid restriction. for 24-48 hours
- Second Line Treatment - Vaptons (Vasopressin receptor antagonists) if fluid restriction ineffective after 24 to 48 hours.
- Finally, treat the root cause. (cancer?)
male hypogonadism
HPG axis
anterior pituitary
leydig cells and sertoli cells in testes.
HPG
Sertoli cells
Sertoli cells are a type of sustentacular “nurse” cell found in human testes which contribute to the process of spermatogenesis
HPG
Leydig cells
produec testosterone in the presence of LH
HPG
primary hypogonadism
f the condition is “Primary” the problem you will see is with the gonads themselves. In other words, the gonads do not produce enough sex hormone to suppress the Pituitary’s secretion of FSH and LH. In this condition you will see an increased FSH and LH in an attempt to stimulate the gonads.
problem in the gonads (leydig not producing enough testosterone.) will see elevated FSH and LH with low testoserone
HPG
Secondary hypogonadism
If the condition is “Secondary” the problem lies either with the Hypothalamus not producing enough GnRH or failure of the Pituitary to respond to the secretion of LSH or FSH. This type of hypogonadism will commonly be observed as one of many Pituitary deficiencies.