24.5 Phys: Thyroid function in health and disease

Question 1

What regulates calcium metabolism?

Answer 1

Calcitonin produced by the thyroid

Question 2

Where are T3 and Calcitonin formed?

Answer 2

T3: colloid
Calcitonin: C cells

Question 3

What are the steps in thyroid hormone synthesis?

Answer 3

1. Follicular cell: enzymes/thyroglobulin synthesis
2. Na+/I- brings I- into the cell. Pendrin moves I- into the colloid
3. Enzymes add I- + Tyrosine= T3, T4
4. Thyroglobulin: taken back into cell (vesicles)
5. Intracellular enzymes separate T3, T4 from the protein
6. T3/T4 (unbound) enter the circulation

Question 4

What are the ratios of T3:T4 produced? Which is more potent?

Answer 4

T3: 10% (most potent)
T4: 90%

Question 5

What happens to TSH in primary and secondary hypothyroidism?

Answer 5

1: TSH increased
2: TSH decreased (no goiter)

Question 6

What happens in hyperthyroidism?

Graves (primary), secondary and tumour

Answer 6

Graves: Increased T3/T4, decreased TSH
2: Increased T3/T4, TRH/TSH
Tumour: Increased T3/T4 Decreased TSH (no goiter)