21. Metabolic Rate Control

Question 1

How does the excess growth hormone differ between children & adults?

Answer 1

Children = gigantism
Adults = acromegaly - thick bones, tissues overgrow

Question 2

How does growth hormone deficiency differ between children & adults?

Answer 2

Children = dwarfism
Adults = no obvious disease. But giving them GH increases lean body mass and vigour

Question 3

Where are signals driving growth hormone expression integrated?

Answer 3

Hypothalamus

Question 4

What hormones increase and supress growth hormone secretion from the anterior pituitary gland?

Answer 4

GRH = Increase
Somatostatin = Suppress

Question 5

Growth hormone is secreted in pulses and more is secreted during the day.
True or False?

Answer 5

FALSE

more is secreted at night during sleep.

Question 6

Growth hormone increases blood glucose levels. What are its immediate effects on metabolism?

Answer 6

Liver: ↑ gluconeogenesis
Fat: ↑ lipolysis
Muscles: ↓ glucose uptake
Insulin resistance

Question 7

Identify 4 hormones which affect growth.

Answer 7

1. Growth hormone
2. Insulin
3. Steroids
4. Thyroid hormones

Question 8

T3 has a longer half-life than T4.

True or False?

Answer 8

FALSE
T4 = 8 days
T3 = 1 day (most active form)

Question 9

What is the difference between TSH and TRH?

Answer 9

TRH (thyroid releasing hormone) = produced by hypothalamus to release TSH from anterior pituitary gland
TSH (thyroid stimulating hormone) = induces thyroid hormone production from thyroid gland

Question 10

Which of these is NOT a function of thyroid hormone?

1. Heat generation
2. Decreasing metabolic rate
3. Growth & Development
4. Increasing metabolic rate

Answer 10

2. Decreasing metabolic rate

Question 11

Where is the thyroid found in the body?

Answer 11

Neck, anchored to thyroid cartilage.

Moves when swallowing.

Question 12

What hormone is responsible for nearly all steps in thyroid hormone production?

Answer 12

TSH

Question 13

How is T4 de-iodinated to T3?

Answer 13

2 enzymes:
Type I - found in liver, kidney, thyroid
Type II - found in pituitary, CNS, placenta

Question 14

How does the thyroid hormone increase heat production?

Answer 14

Does metabolic reactions for the fuck of it.
↑ gluconeogenesis / ↑ glycogenolysis
↑ lipogenesis / ↑ lipolysis
↑ proteolysis / ↑ protein synthesis (wastes muscle overall)

Question 15

Thyroid hormone is crucial for brain development and growth.

True or False?

Answer 15

TRUE

Question 16

How can autoimmunity cause hypo & hyperthyroidism?

Answer 16

Antibodies against TSH receptor can activate it and drive excess TH production. (hyperthyroidism)
Antibodies can destroy TSH receptors. (hypothyroidism)

Question 17

What is the main natural glucocorticoid in humans?

Answer 17

Cortisol

Question 18

How is cortisol production induced?

Answer 18

1. Hypothalamus integrates stress signals to release CRH (corticotrophin releasing hormone).
2. CRH stimulates ACTH (adrenocorticotrophin) release from anterior pituitary gland.
3. ACTH stimulates adrenal cortex to produce cortisol.

Question 19

What is the acute metabolic effect of glucocorticoids?

Answer 19

Increases blood glucose levels and targets this to the brain.

1. ↑ glucogenogenesis in liver
2. ↑ lipolysis
3. ↑ muscle breakdown for gluconeogenesis

Question 20

What are glucocorticoids used for clinically?

Answer 20

Immunosuppression - reduces inflammation