What are the Two Thyroid hormones?
Which has the longer half life? Stronger acting?
Thyroxine (T4) and Triiodothyronine (T3)
T4 has a longer half life
T3 4X more potent
What is Graves disease?
What is Hashimoto's
- Hyperthyroidism- It is an autoimmune disease--> excess in Thyroid hormones
What are the Clinical Features of :
- Heat intolerance
- increased basal metabolic rate
- Cold intolerance
- Decreased Deep tendon reflex
- increased cholesterol
How is Thyroxine metabolized?
What does it?
difference between inner and outer ring?
It is Deiodinated
Inner ring --> inactive reverse T3
Outer ring--> active T3
What inhibits 5'-monodeiodinase?
What does this do?
High does propylthiouracil
- prevents the conversion of T4 to T3
From the Blood, what is the mechanism of Thyroid hormones?
-T4 dissociate from thyroxine binding globulin in plasma before entry into cells.
-In the cells, T4 is enzymatically deiodinated to T3 which enters nucleus and attaches to specific receptors which promotes protein synthesis.-->
What converts I- to Thyroglobulin?
What inhibits it?
- Peroxidase and H2O2
- Iodides and Thioamides
What enzyme prevents the release of T3/T4 from the Thyroid Follicle?
Iodides inhibit the Proteolysis of the Conjugated Thyroglobin
What drugs do the following:
Inhibition of hormone synthesis?
Blockade of hormone release?
T4 to T3 inhibitors?
What are anion inhibitors?
-Propylthiouracil and Methimazole.
-They prevent the uptake of Iodine into the thyroid follicle. They are TOXIC
Name the ANTI-thyroid Thioamides
What do they do?
Which is more potent?
How soon till it works?
Which do you use in pregnancy?
Other uses ?
they inhibit Peroxidase
Methimazole is more potent so it can be used once a day.
Works in about 3 weeks. this is because the Thyroid Follicle has alot of Thyroid hormones stored.
- Propylthiouracil, is safe for use during pregnancy.
- Can be used in Prep for Surgery (decrease size of tumor)
What are some adverse effects of Thioamides?
-maculopapular rash, arthralgia and vasculitis.
-Agranulocytosis – reversible.
What is Potassium Iodide?
What does it do?
What are some uses?
Is it slow acting?
is it used long term?
It is an Anti-thyroid Drug. an Inorganic iodide
It Blocks the organification and release through inhibition of Proteolysis
It decrease the size and vascularity – used before surgery preoperatively. and in thyroid storm treatment.-It is Fast Acting
-It is not for long term as gland ‘escapes’ from its effect.
What are some adverse effects of
-Chronic use in pregnancy-->fetal goiter.
-Iodine induced thyrotoxicosis (Jod Basedow’s phenomenon) at low doses.
-salivary gland inflammation and acne.
What is Radioactive Iodine?
What is its mechanism?
What is a 100% side effect?
When is this treatment contraindicated?
-It is a I-131 isotope is used in treatment of thyrotoxicosis and cancer while others are used in diagnosis.
- Given to patients--> Thyroid cells take it up--> in about 1-3 months -->emission of beta rays which destroys the thyroid gland. (IRREVERSIBLE)- Patients become Hypothyroid (treat with replacement theropy).