Question

Aaron, 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 half a year, but he had attributed this to stress. He has lost considerable weight and, strangely, his skin looks tanned, 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 Aaron does not have anemia, but his plasma glucose, cortisol, and Na⁺ are low, and his plasma K⁺ is high. His doctor orders an ACTH stimulation test, in which Aaron's secretion of cortisol is measured after he is given a synthetic form of ACTH.
(a) What would account for Aaron's low plasma Na⁺ and high plasma K⁺ ?
(b) What is the reason for doing an ACTH stimulation test?
(c) Which gland is primarily affected if ACTH does not cause a normal elevation of cortisol secretion? What is this abnormality called?
(d) Which gland is primarily affected if ACTH does cause an elevation of cortisol secretion?

Accepted Answer

Step 1: Understand the physiological roles of sodium (Na⁺) and potassium (K⁺) in the body, particularly how aldosterone, a hormone produced by the adrenal cortex, regulates their plasma levels by promoting Na⁺ retention and K⁺ excretion in the kidneys. Low plasma Na⁺ and high plasma K⁺ suggest a deficiency in aldosterone secretion or action. Step 2: Recognize that the ACTH stimulation test is used to evaluate the function of the adrenal cortex by measuring cortisol secretion in response to synthetic ACTH. This helps differentiate whether the problem lies in the adrenal glands themselves or in the pituitary gland that produces ACTH. Step 3: If ACTH administration does not increase cortisol secretion, it indicates a primary adrenal gland problem (adrenal insufficiency), where the adrenal cortex is damaged or dysfunctional and cannot produce cortisol properly. This condition is known as Addison's disease. Step 4: If ACTH administration does cause an increase in cortisol secretion, it suggests that the adrenal glands are functioning normally, and the problem is likely secondary, originating from the pituitary gland (which may not be producing enough ACTH under normal conditions). Step 5: Summarize the clinical picture: Aaron's symptoms and lab results (low cortisol, low Na⁺, high K⁺, low blood pressure, weight loss, and hyperpigmentation) point toward primary adrenal insufficiency, where aldosterone deficiency explains the electrolyte imbalance, and the ACTH stimulation test helps confirm the diagnosis and localize the dysfunction.

비슷한 문제에 대한 검증된 영상 답변:

주요 개념

Adrenal Cortex Function and Electrolyte Balance

ACTH Stimulation Test and Its Diagnostic Role

Primary vs. Secondary Adrenal Insufficiency