Hyper and Hypo-Thyroidism Flashcards
Three types of thyroid hormones?
Thyroxine (T4) Triiodothryonine (T3) Reverse Triiodothryonine (rT3)
What thyroid hormone is produced the most?
T4 (90%)
What is the more potent thyroid hormone?
T3 (10x more)
In tissue, what turns T4 to T3?
5-deiodinase
Where are T3/T4 synthesized?
In the colloid of follicular cells
On what molecule are T3/T4 synthesized?
A large tyrosine-rich glycoprotein called thyroglobulin
How is iodide transported into the follicular cells?
Na/I cotransporter
What turns I- into I2?
Thyroid peroxidase
How is I2 conjugated onto tyrosine of thyroglobulin?
By thyroid peroxidase forming MIT and DIT
Thyroid peroxidase also couples MIT and DIT what do they form?
MIT + DIT = T3
DIT + DIT =T4
Where is iodinated thyroglobulin stored?
In the colloid of the follicular cells
What occurs to T4?
It is activated to more potent T3 in target cells
Where does T3 bind?
To both an extracellular and an intracellular receptor
5 physiologic effects of thyroid hormone?
Growth CNS development Skeletal/Cardiac muscle Central sympathetic nervous stimulation Upregulates lipid, carbohydrate, oxidative metabolism, protein synthesis
What are the four thyroid replacement drugs?
Levothyroxine (drug of choice)
Liothyronine
Liotrix
Desiccated thyroid
What is Levothyroxine?
T4
What is Liotrix?
T3 + T4
What is Liothyronine?
T3
What is desiccated thyroid?
Porcine thyroid
What is a potential SE of desiccated thyroid?
Antibodies forming against the porcine
What are the drug overdose SE of thyroid replacement drugs?
High sympathetic tone
What test can Liothyronine used for?
TSH suppression test
What are the 5 classes of anti-thyroid drugs?
Radioactive iodides Anion inhibitors Beta blockers Iodides Thioamides
What are the radioactive iodides?
131 I
What are the anion inhibitors?
Perchlorate
Pertechnetate
Thiocyanate
What are the Thioamides?
Methimazole
Propylthiouracil
How do Thioamides work?
Inhibit synthesis but not release by inhibiting thyroid peroxidase
When to use Thioamides?
Grave’s Disease in children
Propylthiouracil: 1st trimester
Methimazole: 2nd and 3rd trimester
How do anion inhibitors work?
Competitively inhibit iodine uptake by follicular cells
How do the Iodides work?
Inhibits thyroid hormone release
Two possible effects from giving iodides?
Jod-Basedow Effect
Wolff-Chaikoff Effect
(opposites of each other)
What occurs in the Jod-Basedow effect?
Severe hyperthyroidism when a TSH stimulated thyroid suddenly receives an increased in iodine (body didn’t have any Iodine and TSH was high so kick stated thyroid gland)
What occurs in the Wolff-Chaikoff effect?
Temporary suppression of acute hyperthyroidism by increased iodine intake
What does 131 I do?
Burns out half of the thyroid; long term treatment of hyperthyroidism
What do you never treat hyperthyroidism with?
Only a beta blocker! (malpractice lawsuit)
What are the signs of thyroid storm?
Fever
Sympathetic nervous system storm
Confusion/delirium
NVD
Thyroid storm treatment?
IV beta blocker (propranolol)
IV Propylthiouracil
Iodides
Glucocorticoids (inhibit peripheral T4->T3)
What are two iodides given?
Lugol’s solution
KI
