Textbook Question
What effects does parathyroid hormone have on blood calcium level?
519
views
1
rank
16. The Endocrine System
Hormone Review Table
2:06 minutesProblem 26
Textbook 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?
Verified step by step guidance1
Step 1: Analyze Aaron's symptoms and lab results. His symptoms include nausea, chronic fatigue, weight loss, and tanned skin despite limited sun exposure. His lab results show low plasma glucose, cortisol, and Na⁺, along with high plasma K⁺. These findings suggest a disruption in adrenal gland function, which regulates these parameters through hormones like aldosterone and cortisol.
Step 2: Address part (a): Low plasma Na⁺ and high plasma K⁺ are likely due to insufficient secretion of aldosterone, a hormone produced by the adrenal cortex. Aldosterone promotes Na⁺ reabsorption and K⁺ excretion in the kidneys. Without adequate aldosterone, Na⁺ is lost in urine, and K⁺ accumulates in the blood.
Step 3: Address part (b): The ACTH stimulation test is performed to determine whether Aaron's adrenal glands can respond to ACTH (adrenocorticotropic hormone) by producing cortisol. This test helps differentiate between primary adrenal insufficiency (a problem with the adrenal glands themselves) and secondary adrenal insufficiency (a problem with ACTH production by the pituitary gland).
Step 4: Address part (c): If ACTH does not cause a normal elevation of cortisol secretion, the primary issue lies in the adrenal glands. This condition is called Addison's disease, a form of primary adrenal insufficiency where the adrenal glands fail to produce sufficient cortisol and aldosterone.
Step 5: Address part (d): If ACTH does cause an elevation of cortisol secretion, the primary issue lies in the pituitary gland or hypothalamus. This would indicate secondary adrenal insufficiency, where the adrenal glands are functional but are not receiving adequate stimulation due to insufficient ACTH production.
Verified video answer for a similar problem:This video solution was recommended by our tutors as helpful for the problem above
Video duration:
2mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Adrenal Insufficiency
Adrenal insufficiency occurs when the adrenal glands do not produce adequate amounts of steroid hormones, particularly cortisol. This condition can lead to symptoms such as fatigue, weight loss, and electrolyte imbalances, including low sodium (Na⁺) and high potassium (K⁺) levels. In Aaron's case, the combination of low plasma Na⁺ and high plasma K⁺ suggests a disruption in aldosterone production, which is crucial for sodium retention and potassium excretion.
Recommended video:
4:04
Splanchnic Nerves and the Adrenal Medulla
ACTH Stimulation Test
The ACTH stimulation test is a diagnostic procedure used to assess the function of the adrenal glands by measuring cortisol levels after administration of synthetic adrenocorticotropic hormone (ACTH). A normal response would show an increase in cortisol levels, indicating healthy adrenal function. In contrast, a lack of response may suggest primary adrenal insufficiency, where the adrenal glands are unable to produce cortisol despite stimulation.
Recommended video:
2:47The Testes
Primary vs. Secondary Adrenal Insufficiency
Primary adrenal insufficiency, also known as Addison's disease, occurs when the adrenal glands are damaged and cannot produce sufficient hormones. Secondary adrenal insufficiency results from inadequate ACTH production by the pituitary gland, leading to insufficient cortisol production. In Aaron's scenario, if ACTH administration does not elevate cortisol levels, it indicates primary adrenal insufficiency, while a normal response would suggest secondary causes.
Recommended video:
6:59Primary and Secondary Response of Adaptive Immunity
13:6mWatch next
Master Review of Major Hormones with a bite sized video explanation from Bruce Bryan
Start learningRelated Videos
Related Practice