Scan, a 42 year-old single father, goes to his physician complaining of nausea a
ID: 3473508 • Letter: S
Question
Scan, a 42 year-old single father, goes to his physician complaining of nausea and chronic fatigue. He reports having felt fatigued and listless for about six months but he had attributed it to stress. He has lost considerable weight and strangely, his skin has a healthy tan even though he spends long hours at work and rarely ventures outside. His doctor finds very low blood pressure and a rapid, weak pulse. Blood tests show that Scan does not have anemia but his plasma glucose, Cortisol, and Na+ are low whereas his plasma K+ is high. His doctor orders an ACTH stimulation test to measure his secretion of Cortisol after being given a synthetic form of ACTH. a) What would account for Sean's low plasma Na+ and high plasma K+? b) What is the reason for doing an ACTH stimulation test? c) What gland is primarily affected if ACTH does not cause a normal elevation of Cortisol secretion? d) What is this abnormality called? e) What gland is primarily affected if ACTH does cause an elevation of Cortisol secretion?Explanation / Answer
a. Sean might be having Addison's disease which is a hyposecretory disorder of adrenal cortex affecting secretion of mineralocorticoids and glucocorticoids. The primary mineralocorticoid, aldosterone is responsible for promoting Na+ absorption coupled to K+ secretion in the nephron. The hyposecretion of aldosterone is responsible for elevated plasma K+
b. An ACTH stimulation test allows differentiating between a pituitary insufficiency of ACTH secretion or an adrenal insensitivity or insufficiency.
c. The problem originates from the adrenal glands due to which ACTH does not cause elevation of cortisol.
d. The abnormality is called as Addison's disease.
e. When ACTH does not cause an elevation of cortisol secretion it can be likely a tumor or malignancy within the anterior pituitary.
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