Term
| What 3 hormones does the thyroid gland secreat |
|
Definition
1.Thyroxine- T4
2.Triiodothyronine-T3
3.Calcitonin - Calcitonin produced by C-cells and important in calcium metabolism
|
|
|
Term
How are T3 and T4 synthesised?
Where are they stored?
What is this known as? |
|
Definition
Thyrosine residues + Iodine = monoiodotyrosine (MIT)
2I + Thyrosine = dioiodotyrosine (DIT)
DIT + MIT= T3
2 x DIT= T4
Stored in thyroglobulins in the interior of the follicle - known as coupling
|
|
|
Term
| How is T4 conversion to T3 in the peripheral inhibited? |
|
Definition
Propylthiouracil - especially in the Liver & Kidney
by blocking - 5'deiodinase |
|
|
Term
| What are the possible thyroid abnormalities? |
|
Definition
1.Hypothyroidism
2.Hyperthyroidism
|
|
|
Term
| How is Hypothyroidism treated? |
|
Definition
In hypothyroidism you give synthetic T3 & T4
T4 –Thyroxine sodium - given orally in the mornings
T3-Liothyronine - injectable form - given in emergency cases when an immediate response is required i.e myxodema coma
|
|
|
Term
| How is Hyperthyroidism treated? |
|
Definition
Hyperthyroidism can be due to thyroid gland tumor which hypersecretes thyroid hormone. 1.drugs inhibiting the thyroid hormone synthesis and 2.drugs which destroy the tumors should be given
1.Inhibit hormone synthesis: (antithyroid drugs) Propylthiouracil, Methimazole, Carbimazole
2.Inhibit hormone release: Iodine
3.Destroy thyroid tissues: Radioactive Iodine 131I
4. Give B blockers
|
|
|
Term
Name the antithyroid drugs aka thioamines
MOA?
When are they used? |
|
Definition
Propylthiouricil
Methimazole
Carbimazole
Inhibits peroxidase and prevents oxidation of Iodine leading to
1.Inhibition of iodination of tyrosine residues (thus no MIT or DIT)
2.Inhibition of coupling of iodotyrosine to form T3 and T4
No action on iodine trapping and peripheral
conversion of T4 to T3 (except propylthiouracil)
-Hyperthyroidism |
|
|
Term
| What special MOA does Propylthiouracil have? |
|
Definition
Iodine trapping and peripheral
conversion of T4 to T3
|
|
|
Term
Radioactive iodine (131I)
What is its MOA
When is it used? |
|
Definition
- 131I is concentrated by thyroid,
- incorporated in colloid,
- Emits X-rays and b-particles (rays) from within the follicle,
- causing self distruction self destruction.
Used in:
Toxic nodular goiter
Grave’s disease
|
|
|
Term
| Why are B blockers given in hyperthyroidism? |
|
Definition
|
Beta blockers are used to mask the sympathetic
over activity associated with hyperthyroidism
No effect on synthesis or release of thyroid
hormones
|
|
|
Term
| Which antithyroid drug aka thioamide is safe to use in pregnancy? |
|
Definition
| Propylthiouracil as it is highly protein bound |
|
|
Term
| What is used in thyrotoxicities? |
|
Definition
| IODIDE - pre-operativley to decrease the gland size & vascularity |
|
|
