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.
What drugs do we use for hyperthyroidism in pregnant women?
In first trimester use Propylthiouracil. In second and third use Methimazole (to avoid fetal aplasia cutis).
What drugs do we use in Graves disease?
Propylthiouracil or Methimazole (this one is used a lot more). Can add beta blockers. Use Radioactive iodine as definitive treatment.
What is Toxic adenoma and Multinodular Goiter?
Thyroid has focal patches of hyper-functioning follicular cells working independently of TSH due to mutation in TSH receptors; “Hot nodules”.
What is the Jod-Basedow phenomenon?
Hyperthyroidims caused after administration of iodine or iodide. Mostly seen in patients w/ endemic goiter due to iodine deficiency.
What is Subacute Thyroiditis (de Quervain)?
A type of thyrotoxicosis, it is a focal destruction of thyroid w/ granulomatous inflammation. Associated with females (3:1) and HLA-B35. Thought to be caused by virus infection (Coxackie, Echo, Adeno, Measles). Causes acute febrile state and rapidly enlargement of thyroid; first presents as thyrotoxicosis but later turns to hypothyroidism. Usually self limited.
What is the treatment for Thyroid storm?
Beta blockers. Then use PTU or Methimazole.
What ovarian tumor can present as hyperthyroidism?
Struma ovarii teratoma (contains functional thyroid tissue).
A 35 y.o woman presents w/ diffuse goiter and hyperthyroidism. What are the most likely relative values of TSH and thyroid hormones?
TSH low (b/c the body doesn’t want more thyroid hormones). T3 and T4 are elevated.
What would be the cause of hyperthyroidism with the addition of the following finding: Extremely tender thyroid gland.
Subacute (de Quervain) thyroiditis.
What would be the cause of hyperthyroidism with the addition of the following finding: Pretibial myxedema.
Grave’s disease.
What would be the cause of hyperthyroidism with the addition of the following finding: Pride in recent weight loss, is in the medical profession.
Thyroid hormone abuse.
What would be the cause of hyperthyroidism with the addition of the following finding: palpitation of single thyroid nodule.
Toxic thyroid adenoma.
What would be the cause of hyperthyroidism with the addition of the following finding: palpitations of multiple thyroid nodules.
Toxic multinodular goiter.
What would be the cause of hyperthyroidism with the addition of the following finding: recent study using IV contrast (iodine).
Jod-Basedow phenomenon.
What would be the cause of hyperthyroidism with the addition of the following finding: eye changes; proptosis, edema, injection.
Grave’s disease.
What would be the cause of hyperthyroidism with the addition of the following finding: History of thyroidectomy or radioablation of thyroid.
Too much exogenous thyroid hormone.
How would pregnancy affect serum thyroid hormone levels?
Thyroid binding globulin (TBG) is increased because estrogen increases it. Increased in total T3 and T4. Normal free T4 and T3.
