Thyroid function and dysfunction

Question 1

Describe the H-P-thyroid axis.

Answer 1

Hypothalamus releases TRH.
TRH acts on ant. pituitary.
Ant. pituitary will produce TSH.
TSH acts on thyroid to make T3 and T4.
T3 and T4 have a negative feedback effect on ant. pituitary and hypothalamus.

Question 2

How are T3 and T4 synthesised from tyrosine? And where does this occur?

Answer 2

• Occurs in the thyroid gland.

Question 3

What type of cells are C cells and follicular cells?

Answer 3

Epithelial cells.

Question 4

How is iodine transported into the follicular cells?

Answer 4

Sodium Iodine symporter.

Question 5

What is the function of TPO?

Answer 5

Oxidation of iodine so it can be conjugated.

Question 6

Main effect of T3 and T4.

Answer 6

• Increased metabolic activity.

Question 7

What are thyroid hormones in blood bound to?

Answer 7

• thyroxine binding globulin.
• albumin.
• transthyretin (TTR).

Question 8

What physiological actions do the thyroid hormones increase?

Answer 8

• BMR.
• Cardiac muscle activity.
• SNS.
• Protein synthesis.
• Cerebral activity.
• Action of growth hormone.

Question 9

What are the characteristics features of hypothyroidism?

Answer 9

• tired all the time.
• weight gain bc BMR slowed.
• cold intolerance.
• bradycardia and hypotension.

Question 10

What is the hormone profile for hypothyroidism?

Answer 10

• Low T3.
• Low T4.
• High TSH.

Question 11

What is Hashimoto’s disease?

Answer 11

• Anti TPO antibodies.
  Autoreactive T helper cells that recruit B cells and T killer cells to the thyroid.
  Causes follicular cell destruction –> hypothyroidism.
  However, it can produce an initial hyperthyroid state.

Question 12

What are the features of congenital hypothyroidism?

Answer 12

Coarse appearance/macroglossia (large tongue).
Floppy/poor feedings.
Mental retardation/short stature.

Question 13

Characteristic features of hyperthyroidism.

Answer 13

• Weight loss.
• Tachycardia.
• Heat intolerance.
• Anxiety.
• Goitre.
• Increased oxygen consumption –> breathe heavily.
• Increased protein synthesis.
• Eye signs (exophthalmos).
• Tremor.
• Muscle weakness.

Question 14

What is Grave’s disease?

Answer 14

• causes a hyperthyroid state.
• TSH effects mimicked by Anti-TSH-R antibodies.
• stimulate receptor after binding to it causing increased synthesis of the thyroid hormones.

Question 15

Hormone profile of Grave’s disease.

Answer 15

Low TSH.

High T3 and T4.

Question 16

What are the 4 types of thyroid cancer.

Answer 16

Papillary,
Follicular,
Medullar,
Anapaestic????