End 6 - Thyroid Basics And Hyperthyroidism Flashcards
What is the most common ectopic thyroid tissue site?
The tongue.
What is the clinical presentation of thyroglossal duct cyst?
Middle of neck. Moves w/ swalllowing.
What structure has the most massive bloodflow per gram of organ?
The adrenal. Then the thyroid.
What is organification of the iodine?
Iodine enters the thyroid tissue by Na gradient. Then it is oxidized by peroxidase. Then it is bound to thyroglobulin (a storage protein) (Iodination of thyroglobulin).
Which 2 drugs inhibits the organification of Iodine?
Propylthiouracil and methimazole.
Where is the actual thyroid hormone made?
Inside the iodinized thyroglobulin: iodine molecule added to tyrosine one at a time (monoiodotyrosine) and finished when total of 2 are added to the tyrosine molecule (diiodotyrosine).
What is condensation AKA coupling in thyroid production?
It is the production of T3 and T4. When a monoiiotyrosine is added with a diiodotyrosine, it produces a T3. If two diiodotyrosines are coupled together, they make T4.
How is T3 and T4 released into the bloodstream?
T3 and T4 are stored in the colloid of the thyroid bound to thyroglobulin. In order to be released to the bloodstream, they must be released from the thyroglobulin by proteolysis.
How is most of the T3 and T4 in the bloodstream?
Bound to a protein called Thyroxin Binding Globulin (TBG). Only the free hormone is active.
Which drug inhibits the conversion of T4 to T3 in the periphery?
Propylthiouracil.
What would be the cause of low thyroxine-binding globulin (TBG) levels? How would T3 and T4 be affected?
Hepatic failure, Nephrotic syndrome, or other conditions of low protein. Total T3 and T4 is decreased. However, free T3 and T4 might be unchanged.
What are the properties of T3 and T4?
T3: binds w/ greater affinity, converted from T4 in periphery, has short half-life. T4: Produced in greater quantity, has long half-life.
How are the TSH levels in Hyperthyroidism?
They are low, because the body does not want more thyroid hormones. They are high in hypothyroidism.
What is the most common cause of hyperthyroidism?
Grave’s disease.
What is Grave’s disease?
An autoimmune disorder, Thyroid-stimulating immunoglobulin (TSI, which is an IgG antibody), binds to TSH receptors causing stimulation of the thyroid gland to release T3 and T4. This leads to low TSH. Associated with females(4:1) and HLA-DR3 and HLA-B8. Causes exophthalmos, pre-tibial mixedema on top of hyperthyroidism symptoms.