Lecture 5

Question 1

Anatomy of the thyroid gland.

Answer 1

Question 2

What is the function of calcitonin?

Answer 2

decreases blood calcium levels

Question 3

What increases blood calcium levels?

Answer 3

Parathyroid

Question 4

Thyroid hormones are made from iodine and tyrosine

Answer 4

Question 5

Thyroid hormones

Answer 5

Long-term effects on metabolism
Not essential for life; essential for normal growth and development in children
Amine hormone – tyrosine & iodine

Question 6

Synthesis of thyroid hormone:

Answer 6

Follicle (acini)
Glycoprotein mixture – colloid
2-3 months supply of thyroid hormone at one time

Question 7

more T4 in plasma
85% T4 is converted to T3 at target cells (deiodinase)
Transport in blood: bound to thyroxine-binding globulin and albumin

Question 8

Iodine in the thyroid gland is found as

Answer 8

Iodide (I-)

Question 9

Answer 9

Thyroglobulin:

T3:
[Tyrosine - (2 I-)] + [Tyrosine - (1 I-)]

T4:
[Tyrosine - (2 I-)] + [Tyrosine - (2 I-)]

Question 10

Question 11

Effects of thyroid hormone (1)

Answer 11

Main determinant of basal metabolic rate
- Affects every tissue in body
- Receptor 10x greater affinity for T3
- Slow reaction of hormone – response after several hours and maximal response after several days
- Duration of response: days to weeks

Question 12

Tyrosine acts like a steroid hormone - uses receptors and transported in blood

Question 13

Effects of thyroid hormone (2)

Answer 13

• Influences synthesis and degradation of carbohydrate, fat, and protein
  Regulator of body’s rate of O2 consumption and energy expenditure under resting conditions
  Calorigenic effect: increased metabolic activity results in increased heat production
• Increases target-cell responsiveness to catecholamines (sympathomimetic)
• Increases heart rate and force of contraction
• Essential for normal growth (GH & IGF-I)
• Plays crucial role in normal development of nervous system

Question 14

Thyroid hormones affect quality of life

Answer 14

Main function: provide substrates for oxidative metabolism
Thermogenic
+ O2 consumption
Interact with other hormones – modulate protein, carbohydrate and fat metabolism

Question 15

Thyroid hormone in children

Answer 15

necessary for full expression of growth hormone (permissive)
- Essential for normal growth & development
- Nervous system:
Myelin & synapse formation requires T3 & T4
Regulate microtubule assembly – essential for neuronal growth

Question 16

The thyroid gland of a 5-year old boy is transplanted from its normal position in the neck to the abdomen (between the kidneys). Assume that the gland develops a good blood supply in its new position, and that it remains alive.
List the abnormalities that will develop in this child:
i. after one month.
ii. after 10 years.

Answer 16

Nothing - cause connected to a blood supply

Question 17

The thyroid gland of a 5-year old boy is surgically removed. Assume that he receives no therapy after the operation.
List the abnormalities that will develop in this child:
i. after one month
ii. after 10 years

Answer 17

i.) No abnormalities - TH have long lasting effects (up to 2 months)

ii.) stunted growth, nervous system abnormalities