Hormonal Control of Urine Production and Diuretics

Vocabulary flashcards covering hormonal control of body fluids, sodium and potassium regulation, endocrine disorders (Conn's, Cushing's, Addison's), and various classes of diuretics (Mannitol, Furosemide, Thiazides, Spironolactone, Amiloride).

Total body water

Approximately $60\%$ of total body weight, divided into intracellular fluid ($40\%$) and extracellular fluid ($20\%$).

Extracellular fluid (ECF)

Fluid compartment outside of cells consisting of interstitial fluid and plasma, representing $20\%$ of total body weight.

Isosmotic volume contraction

A condition where fluid and solutes are lost from plasma (e.g., diarrhea or burns) but blood osmolarity remains unchanged, causing hematocrit and protein concentration to increase.

Hyperosmotic volume contraction

A state caused by sweating, dehydration, or diabetes insipidus where mostly water is lost, leading to decreased plasma volume, increased plasma osmolarity, and cell crenation.

Hypoosmotic volume contraction

Occurs in conditions like Addison’s disease where the loss of sodium and water reduces blood osmolarity, leading to water moving into cells and increasing Mean Corpuscular Volume ($MCV$).

Isosmotic volume expansion

The addition of isosmotic fluid to plasma, such as an infusion of isotonic $NaCl$, which increases ECF volume while decreasing hematocrit and protein concentration.

Hyperosmotic volume expansion

Increased plasma volume and osmolarity typically caused by high $NaCl$ intake or Conn's/Cushing's disease, resulting in water moving from cells to plasma until equilibrium is reached.

Hypoosmotic volume expansion

Volume expansion caused by excessive $ADH$ ($SIADH$), leading to water retention, reduced osmolarity, and water moving into cells until equilibrium is achieved.

Atriopeptin (ANP)

Atrial natriuretic peptide that increases $GFR$ and decreases $Na^+$ reabsorption to promote sodium excretion.

Aldosterone

A hormone triggered by hyperkalemia or the $R-A-A$ system that increases $Na^+$ reabsorption in the principal cells of the late $DCT$ and promotes $K^+$ secretion.

Acute Acidosis

A state where $H^+$ enters cells and $K^+$ leaves, resulting in hyperkalemia because intracellular $H^+$ reduces the activity of the $Na^+/K^+$ pump.

Chronic Acidosis

Acidosis lasting several days that inhibits $NaCl$ and water reabsorption at the $PCT$, leading to increased flow at the $LDCT$ which stimulates and results in potassium loss.

Conn’s disease

Primary aldosteronism characterized by hypernatremia, hypokalemia, and hypertension.

Cushing’s syndrome

Primary hyperadrenalism involving excess aldosterone, androgens, and glucocorticoids, often resulting in hypernatremia, hypokalemia, and high blood sugar levels.

Addison’s Disease

Primary adrenal insufficiency featuring low aldosterone and glucocorticoids, resulting in hypotension, hyponatremia, hyperkalemia, and mild acidosis.

Goldblatt (renal) hypertension

Secondary hypertension caused by inappropriate renin release, often due to decreased Renal Blood Flow ($RBF$) or low $GFR$, leading to a hypertrophied heart muscle.

Diabetes mellitus

A condition where unreabsorbed glucose in the kidney tubules causes osmotic diuresis, leading to polyuria, glucosuria, ketonuria, and polydipsia.

Mannitol

An osmotic diuretic administered IV that is freely filtered at the $PCT$ but not reabsorbed, forcing water to stay in the tubule to maintain osmolarity.

Furosemide (Lasix)

A potent diuretic that inhibits $Na^+K^+Cl^-$ transporters in the thick ascending limb of the loop of Henle, eliminating the medullary interstitial gradient.

Thiazides

Diuretics that work at the early distal convoluted tubule by inhibiting $Na/Cl$ transporters to prevent salt and water reabsorption.

Spironolactone

A potassium-sparing diuretic and aldosterone antagonist that reduces the number of basolateral $Na/K$ pumps in the late $DCT$; can cause hyperkalemia or gynecomastia.

Amiloride

A potassium-sparing diuretic that blocks $Na^+$ channels on luminal membranes in the late $DCT$ and collecting tubules.