Passage
A 6-day-old, genotypically normal (46,XX) female patient shows symptoms of hypoglycemia (low blood glucose) and hypotonia (decreased muscle tone). Physical examination reveals abnormal development of the external genitalia, and laboratory studies show elevated urinary sodium content, increased serum levels of potassium, and abnormal serum concentration of several steroid hormones. The patient is diagnosed with 21-hydroxylase deficiency, the most common type of congenital adrenal hyperplasia (CAH).CAH refers to a group of autosomal recessive diseases, each associated with defective production of one or more steroid hormones by the adrenal glands, two crescent-shaped glands located above each kidney in the abdominal cavity. It has been reported that unequal crossing over involving chromosome 6 can result in CAH. More than 90% of CAH diagnoses are associated with a deficiency of 21-hydroxylase, an enzyme encoded by the CYP21A2 gene on chromosome 6.Normally, 21-hydroxylase catalyzes chemical reactions involved in the synthesis of aldosterone and cortisol, the principal mineralocorticoid and glucocorticoid hormones, respectively. As a result, patients with 21-hydroxylase deficiency exhibit diminished serum levels of aldosterone and cortisol. However, synthesis and secretion of the sex hormone testosterone is excessive. Glucocorticoid deficiency disrupts the negative feedback loop linking the brain to the adrenal gland, leading to hyperplasia (increased cell proliferation) of adrenal tissue.The patient's 21-hydroxylase deficiency is treated with regular administration of synthetic steroid hormones. Her condition improves after receiving these medications.
-What changes in blood volume and serum sodium content would be expected as a result of using synthetic hormones to replenish aldosterone in CAH patients?

Question

Passage
A 6-day-old, genotypically normal (46,XX) female patient shows symptoms of hypoglycemia (low blood glucose) and hypotonia (decreased muscle tone).  Physical examination reveals abnormal development of the external genitalia, and laboratory studies show elevated urinary sodium content, increased serum levels of potassium, and abnormal serum concentration of several steroid hormones.  The patient is diagnosed with 21-hydroxylase deficiency, the most common type of congenital adrenal hyperplasia (CAH).CAH refers to a group of autosomal recessive diseases, each associated with defective production of one or more steroid hormones by the adrenal glands, two crescent-shaped glands located above each kidney in the abdominal cavity.  It has been reported that unequal crossing over involving chromosome 6 can result in CAH.  More than 90% of CAH diagnoses are associated with a deficiency of 21-hydroxylase, an enzyme encoded by the CYP21A2 gene on chromosome 6.Normally, 21-hydroxylase catalyzes chemical reactions involved in the synthesis of aldosterone and cortisol, the principal mineralocorticoid and glucocorticoid hormones, respectively.  As a result, patients with 21-hydroxylase deficiency exhibit diminished serum levels of aldosterone and cortisol.  However, synthesis and secretion of the sex hormone testosterone is excessive.  Glucocorticoid deficiency disrupts the negative feedback loop linking the brain to the adrenal gland, leading to hyperplasia (increased cell proliferation) of adrenal tissue.The patient's 21-hydroxylase deficiency is treated with regular administration of synthetic steroid hormones.  Her condition improves after receiving these medications.
-What changes in blood volume and serum sodium content would be expected as a result of using synthetic hormones to replenish aldosterone in CAH patients?

Quizplus · Accepted Answer

11ecba2d_0fce_0ff2_a3bf_894a759a39a9_MD0008_00 Located in the posterior abdomen on the left and right sides of the body, the kidneys are two bean-shaped organs that participate in excretory, metabolic, and homeostatic functions. The homeostatic functions of the kidneys occur primarily through the filtration of blood and the selective secretion or reabsorption of filtered contents. Filtration of blood by the kidneys yields a fluid (called the filtrate) that undergoes significant changes in volume and composition prior to excretion as urine. Nutrients such as glucose and amino acids are reabsorbed into the body, and toxins are secreted. The majority of filtered sodium (Na⁺) and water (H₂O) is reabsorbed. However, the reabsorption of sodium and water is subject to some degree of adjustment based on physiological conditions. For example, the hormone aldosterone, which is secreted by the adrenal cortex in response to high serum potassium (K⁺) and low blood pressure (via the renin-angiotensin system), acts on the kidney to promote sodium reabsorption and potassium secretion. However, more sodium is reabsorbed than potassium is secreted. Consequently, an ion gradient is generated between the filtrate and the interstitial fluid in the adjacent interstitial space, causing water to be reabsorbed into the interstitial fluid (and eventually the bloodstream) via osmosis. As a result, blood volume and therefore blood pressure increase. According to the passage, patients with congenital adrenal hyperplasia (CAH) exhibit deficient synthesis and secretion of aldosterone. After administering synthetic aldosterone, increased sodium and water reabsorption by the kidneys will result in increased blood volume and increased serum sodium content. (Choices B and D) Aldosterone promotes the reabsorption of sodium by the kidneys, leading to increased serum sodium content. (Choices C and D) Aldosterone promotes the reabsorption of water by the kidneys (a side-effect of the reabsorption of sodium), leading to increased blood volume. Educational objective: Aldosterone is secreted by the adrenal cortex in response to elevated plasma potassium and decreased blood pressure. Aldosterone acts on the kidneys to increase the reabsorption of sodium, which in turn leads to increased reabsorption of water and, ultimately, increased blood volume and pressure.

Passage a 6-Day-Old, Genotypically Normal (46,XX) Female Patient Shows Symptoms of of Hypoglycemia