HPA/HPT axis critical thinking

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• TSH

• Natural T3/T4

• Thyroid Gland Size

1. If a patient were given artificial T3 and T4 over time, how would this probably affect their:

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• cortisol levels

• ACTH levels

2. If a patient’s ACTH receptors on her adrenal glands were mutated and non-functioning, how would this affect their

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• Thyroid gland size

• T3/T4 levels

3. If a patient had a pituitary tumor that caused the pituitary to release abnormally high amounts of TSH, how would this affect their

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• Cortisol levels

4. If someone is really stressed out, how would this affect his

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• Metabolism

• T3/T4 levels

• TSH levels

5. If a patient’s antibodies in their bloodstream were attaching to and overstimulating TSH receptors in the thyroid, what would happen to the patient’s

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• TSH levels

• T3/T4 levels

6. If a patient’s T3 and T4 receptors on her pituitary gland were blocked, how would this affect her

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• T3/T4 levels

• TSH levels

7. If a patient had hypothyroidism, a condition where the thyroid gland is under producing T3 and T4, what results would you expect if you measured his T3 and T4 levels and TSH levels? Assume that the problem is in the thyroid, not the pituitary.

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• CRH levels

• ACTH levels

8. If a patient were given artificial cortisol supplements, what effect would this likely have on her

This is because the artificiall T3/T4 would bind to T3/T4 receptors on the anterior pituitary to cause negative feedback. The anterior pituitary would respond by producing less TSH.

TSH would decrease

This is because the artificial T3/T4 would bind to T3/T4 receptors on the anterior pituitary. This would cause negative feedback and reduce TSH production. If TSH is reduced, there will be less stimulation of the thyroid and, thus, less natural T3/T4 production

Natural T3/T4 would decrease

This is because the artificial T3/T4 would bind to T3/T4 receptors on the anterior pituitary. This would cause negative feedback and reduce TSH production. Reduced TSH means that the thyroid will not be stimulated as much which will cause the gland to atrophy (decrease in size)

Thyroid gland size would decrease

If the ACTH receptors on the adrenal glands are mutated and nonfunctioning, they won't be able to bind to ACTH. If ACTH cannot bind, then there will be no signal for the adrenal glands to produce cortisol.

Cortisol levels would decrease

If ACTH is unable to bind to receptors on the adrenal glands, then there is not cortisol production. Without cortisol production, there is no negative feedback. Therefore, the anterior pituitary "thinks" that it needs to produce more ACTH to stimulate cortisol production from the adrenal glands.

ACTH levels would increase

This is because increased TSH will cause increased stimulation of the thyroid. The more stimulated the thyroid, the bigger it will grow

Thyroid gland size would increase

Since the anterior pituitary is producing more TSH, the thyroid (assuming normal function) will respond to that increased TSH by producing more T3/T4

TSH levels would increase

Stress is the stimulus that causes the hypothalamus to produce CRH. This, in turn, stimulates the anterior pituitary to make ACTH. Increased ACTH will then cause the adrenal glands to produce more cortisol as a response.

Cortisol levels will increase

In this scenario, the thyroid is being stimulated by antibodies produced the the patient's own immune system (this is an example of an autoimmune disorder). These antibodies mimic TSH and the thyroid cannot distinguish between the antibodies and real TSH. Therefore, more T3/T4 will be produced which will increase their metabolism.

Metabolism would increase

In this scenario, the thyroid is being stimulated by antibodies produced the the patient's own immune system (this is an example of an autoimmune disorder). These antibodies mimic TSH and the thyroid cannot distinguish between the antibodies and real TSH. Therefore, more T3/T4 will be produced.

T3/T4 levels will increase

In this scenario, the thyroid is being stimulated by antibodies produced the the patient's own immune system (this is an example of an autoimmune disorder). These antibodies mimic TSH and the thyroid cannot distinguish between the antibodies and real TSH. Therefore, more T3/T4 wil lbe produced. T3/T4 will cause negative feedback and bind to receptors on the anterior pituitary to "tell" the anterior pituitary to stop producing TSH.

TSH levels will decrease

If the T3/T4 receptors on the anterior pituitary are blocked, there will be no way for negative feedback to occur. Therefore, the anterior pituitary will never receive the signal to stop producing TSH.

TSH levels would increase

If the T3/T4 receptors on the anterior pituitary are blocked, there will be no way for negative feedback to occur. Therefore, the anterior pituitary will never receive the signal to stop producing TSH. The excess TSH will continue to stimulate the thyroid gland and excessive T3/T4 will be produced

T3/T4 levels will increase

By definition, hypothyroidism means that not enough T3/T4 is being produced (hypo = under/below).

T3/T4 levels would be low

If the thyroid gland is not producing enough T3/T4, there will not be enough thyroid hormones for negative feedback to occur.Since T3/T4 will not bind to the anterior pituitary, the anterior pituitary will continue to produce TSH in an attempt to "tell" the thyroid to make more T3/T4

TSH levels would be high

Artificial cortisol is able to bind to all cortisol receptors. Therefore, it would bind to cortisol receptors on the hypothalamus which would initiate negative feedback and cause a decrease in CRH production

CRH levels would decrease

Artificial cortisol is able to bind to all cortisol receptors. Therefore, it would bind to cortisol receptors on the anterior pituitary which would initiate negative feedback and cause a decrease in ACTH production

ACTH levels would decrease