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Cholesterol is usually converted to progesterone and testosterone - VCE - SSCE Biology - Question 24 - 2010 - Paper 1
Question 24
Cholesterol is usually converted to progesterone and testosterone. Progesterone is then converted to cortisol due to the action of an enzyme 21-hydroxylase. If the e... show full transcript
Worked Solution & Example Answer:Cholesterol is usually converted to progesterone and testosterone - VCE - SSCE Biology - Question 24 - 2010 - Paper 1
Step 1
Describe the role of ACTH in the synthesis of cortisol.
Answer
ACTH (Adrenocorticotropic hormone) plays a critical role in the synthesis of cortisol by stimulating the adrenal cortex. When ACTH is released from the anterior pituitary gland, it binds to receptors on adrenal cortex cells, leading to increased production and release of cortisol. This process is vital for regulating metabolism, immune responses, and the body's stress response.
Step 2
Explain the consequence of a defective 21-hydroxylase enzyme.
Answer
A defective 21-hydroxylase enzyme leads to a decreased synthesis of cortisol and aldosterone. As a result, there is an accumulation of steroid precursors, which are then diverted into the production of androgens, causing excess testosterone. This condition results in congenital adrenal hyperplasia (CAH), which can lead to various health issues, including adrenal crisis and virilization.
Step 3
Outline the steps involved in the ACTH stimulation test.
Answer
The ACTH stimulation test involves the following steps:
- Initial Blood Sample: A blood sample is taken to measure baseline levels of testosterone and cortisol.
- ACTH Injection: A synthetic form of ACTH is injected into the patient to stimulate the adrenal glands.
- Second Blood Sample: After 60 minutes, a second blood sample is taken to measure the levels of cortisol and testosterone post-ACTH administration.
- Analysis: The results are analyzed to determine how well the adrenal glands respond to ACTH under normal conditions compared to baseline levels.