Thyroid Hormones

Question 1

How can insufficient thyroid hormone affect a developing fetus?

Answer 1

• Deficiency in thyroid hormones can leave to underdevelopment of the CNS
• Conduction velocity of peripheral nerves vary directly with the availability of thyroid hormones

Question 2

Cretinism is due to…

Answer 2

Congenital hypothyroidism or maternal iodine deficiency

Question 3

What is the thyroid gland stimulated by?

Answer 3

Pituitary thyroid stimulating hormone (TSH)

Question 4

What hormones is the thyroid gland stimulated by?

Answer 4

TSH, FSH, LH, and hCG or eCG

Question 5

What is the regulation for TSH?

Answer 5

negative feedback for production of pituitary TSH is the product of the thyroid glands (T3 and T4)
is positively regulated by hypothalamic thyrotropin-releasing hormone

Question 6

What mainly regulates metabolic rate?

Answer 6

Thyroid hormones (T4 and /T3); they do not act on a specific tissue but rather all tissues and sensitizes the cell to make it more sensitive to the effect of the hormones

Question 7

Describe how heat is regulated during stress and cold (in infants)

Answer 7

Stress: inhibits the hypothalamus, so not TRH is released, so ant. pit will not release TSH to stimulate thyroid gland to release T3 and T4 (to overall increase metabolic rate and yield heat as a by product)
Cold in infants: stimulates hypothalamus to released TRH, which will activate ant pit to release TSH, which will stimulate the release of T3 and T4 from the thyroid gland to increase metabolic activity and increase body temp

Question 8

How do T3 and T4 increase temp?

Answer 8

By stimulating energy consumption andincreasing heat production; increase the number and activity of the Na/K ATPase pumps
• Hydrolyze ATP
○ ATP decrease
○ Compensated by increasing metabolism of glucose to produce energy
§ Directly increases body temperature due to increased cell metabolism
The hydrolysis of ATP yields heat as a by-product

Question 9

What is the most important regulator of O2 consumption and energy expenditure under resting conditions?

Answer 9

Thyroid hormones

Question 10

What is hypo- and hyperthyroidism?

Answer 10

Hypothyroidism is underactive thyroid and produces a senstation of cold; hyperthyroidism is overactive and produces sensation of warm

Question 11

What leads to metamorphisis in most amphibians or whatever undergoes metamorphosis idk

Answer 11

usually an increase in T4 but agnathan lamprey are the opposite because they require a decrease in T4

Question 12

• Thyroid hormones also contribute to seasonal moultin

○ This leads to a change in plumage of birds and coat colour in mammals

Answer 12

ye