HPA/HPT axis critical thinking

HPT/HPA Axis Critical Thinking Questions

1. Synthroid is a medication that mimics T3/T4 (aka: artificial T3/T4). If a patient were given Synthroid, over time, how would this affect their TSH, natural T3/T4, and thyroid gland size?

• TSH

• Natural T3/T4

• Thyroid Gland Size

increase decrease

increase decrease

increase decrease

2. If a patient had a pituitary tumor that caused the pituitary to release abnormally high amounts of TSH, how would this affect their thyroid gland size and T3/T4 levels?

increase decrease

• Thyroid gland size

• T3/T4 levels

increase decrease

3. If a patient’s antibodies (immune proteins) in their bloodstream were attaching to and overstimulating TSH receptors in the thyroid, what would happen to the patient’s T3/T4 levels, metabolism, and natural TSH levels?

increase decrease

• T3/T4 Levels

• Metabolism

• Natural TSH levels

increase decrease

increase decrease

4. If a patient’s T3 and T4 receptors on their pituitary gland were blocked, how would this affect their TSH and T3/T4 levels

increase decrease

• TSH levels

• T3/T4 levels

increase decrease

5. 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.

Be high Be low

• T3/T4 levels

• TSH levels

Be high Be low

6. A patient is prescribed long-term corticosteroid therapy (artificial cortisol) for an autoimmune condition. How will this affect their CRH, ACTH, and natural cortisol production?

• CRH levels

• ACTH levels

• Natural cortisol levels

increase decrease

increase decrease

increase decrease

7. If a patient’s ACTH receptors on her adrenal glands were mutated and non-functioning (unable to bind to ACTH), how would this affect their cortisol and ACTH levels?

• cortisol levels

• ACTH levels

increase decrease

increase decrease

8. During an abnormally long period of psychological stress, what effects would you expect to see on CRH, ACTH, and cortisol levels?

increase decrease

• CRH levels

• ACTH levels

• Cortisol levels

increase decrease

increase decrease

9. In Addison's disease, where the adrenal glands cannot produce enough cortisol, how would this affect CRH and ACTH production?

• CRH levels

• ACTH levels

increase decrease

increase decrease

10. A patient has a benign tumor on their pituitary gland that prevents ACTH production. How would this affect CRH and cortisol production?

• cortisol levels

• CRH levels

increase decrease

increase decrease

T3/T4 levels will 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

Metabolism would increase

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.

Thyroid gland size would increase

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

Natural TSH levels will decrease

These antibodies mimic TSH and the thyroid cannot distinguish between the antibodies and real TSH. Therefore, more T3/T4 will be produced. T3/T4 will cause negative feedback and bind to receptors on the anterior pituitary to "tell" the anterior pituitary to stop producing its own natural TSH.

ACTH levels will increase

Stress is the stimulus that causes the hypothalamus to produce CRH. This, in turn, stimulates the anterior pituitary to make ACTH.

T3/T4 levels will increase

The antibodies mimic TSH and the thyroid cannot distinguish between the antibodies and real TSH. Therefore, more T3/T4 will be produced.

T3/T4 levels would increase

Since the anterior pituitary is over producing TSH, the thyroid will respond to that increased TSH by producing more T3/T4

T3/T4 levels would be low

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

CRH Levels will increase

If there is not enough cortisol being produced, there will be no negative feedback to the hypothalamus. The hypothalamus will continue to increase CRH production

CRH levels will increase

If the anterior pituitary is not producing ACTH, then the adrenal glands will not get the signal to produce cortisol. If cortisol is not being produced, there will be no negative feedback to the hypothalamus, so the hypothalamus will continue to increase CRH production

Cortisol levels 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.

TSH levels would be high

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

ACTH 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 will increase

If there is not enough cortisol being produced, there will be no negative feedback to the hypothalamus and anterior pituitary The hypothalamus will continue to increase CRH production which will cause the anterior pituitary to continue to produce ACTH.

Natural cortisol levels would decrease

Since the corticosteroids (artificial cortisol) binds to cortisol receptors on the hypothalamus and anterior pituitary glands, there will be no stimulation of the adrenal glands and your own natural cortisol production will decrease

CRH levels would decrease

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

ACTH levels would increase

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.

CRH Levels will increase

Stress is the stimulus that causes the hypothalamus to produce CRH.

Cortisol levels will 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 decrease

Since the anterior pituitary is not producing ACTH, there is no signal to the adrenal glands to produce cortisol.

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.

TSH would decrease

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

Synthroid mimics natural T3/T4

Natural T3/T4 would decrease

This is because the Synthroid 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

Thyroid gland size would decrease

This is because the Synthroid 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)