Thyroid disorders Flashcards
(65 cards)
Define:
1) TRH
2) TSH
1) Released from hypothalamus, stimulates pituitary gland to release TSH
2) Thyroid Stimulating Hormone (TSH): released from anterior pituitary gland, stimulates thyroid gland to make T3 & T4
Define:
1) T4
2) T3
1) Thyroxine (T4): secreted from the thyroid gland
2) Triiodothyronine (T3): mostly formed from peripheral conversion of T4 to T3
With hypothyroidism, __________ is higher than T4
TSH
Thyroid hormone synthesis:
1) What happens in the GI tract?
2) What abt in the blood?
1) Dietary iodine absorbed from GI tract
Enters circulation as iodide
2) Iodide taken from serum into thyroid gland by iodine pump (thyroid concentrates it)
What happens in the thyroid in regards to thyroid hormone synthesis?
1) Iodide is oxidized by the thyroid peroxidase enzyme
2) Binds to tyrosine to form monoiodotyrosine and diiodotyrosine (MIT and DIT)
3) MIT and DIT couple together to form T4 and T3
DIT + DIT = tetraiodothyronine (thyroxine or T4)
DIT + MIT = triiodothyronine (T3)
1) What is a normal TSH lab value?
2) When might a positive Thyroglobulin Antibody (TgAb) test occur?
1) 0.5-4.5 mIU/L
2) +Hashimoto’s
+Graves’
Define the TSH values for the following:
1) Thyrotoxicosis (overt)
2) Subclinical hyperthyroidism
3) Normal range
1) </= 0.1
2) 0.1-0.5
3) 0.5-4.5
Define the TSH values for the following:
1) At risk: repeat TSH at least yearly
2) Subclinical (mild) hypothyroidism
3) Hypothyroidism (overt)
1) 2.5 – 4.5
2) 4.5 – 10
3) >/= 10
List 3 risk factors for hyperthyroidism (thyrotoxicosis)
1) Stress
2) Family history of Graves’ disease
3) Cigarette smoking
True or false: Hypo and hyperthyroidism generally have opposite symptoms
True
Overt Hyperthyroidism: List 2 types & which is most common
1) Graves Disease (most common)
2) Thyroid storm (extreme; an emergency)
Graves disease:
1) What kind of condition is it?
2) List 2 symptoms
1) Autoimmune syndrome
2) Exophthalmos
Pretibial myxedema
How do you prep a patient for a thyroidectomy?
Antithyroid drug for 6-8 weeks
Addition of iodides for 10-14 days
Propranolol (post surgery as well)
Name a pharmacologic therapy for Graves disease
Radioactive iodine
Methimazole (MMI):
1) What is the MOA?
2) What two doses do the tablets come in?
1) Inhibit coupling of MIT and DIT to form T4 and T3
2) 5 & 10 mg tabs
Propylthiouracil (PTU): What are the 2 MOAs?
1) Inhibit coupling of MIT and DIT to form T4 and T3
2) Inhibits peripheral conversion of T4 to T3
Why should you reserve PTU for pts who cannot tolerate MMI?
Boxed Warning for severe liver injury and acute liver failure
PTU:
1) What doses do the tablets come in?
2) How long does it take to work?
1) 50mg tabs
2) Several weeks
List 4 mild side effects of thionamides (MMI + PTU)
1) Skin rash (urticarial reactions) (5%)
2) Arthralgia (5%)
3) Leukopenia (benign, transient) (12%)
4) Lupus-like syndrome (5%)
List and describe the 2 reasons to d/c MMI + PTU
1) Agranulocytosis (0.5-6%)
-ANC < 1,000 / mm3
2) Immunoallergic hepatitis (1.3%)
-Almost exclusive to PTU
How long do you need to monitor TSH & FT4 with MMI/PTU?
4-8 weeks initial, 2-3 months once euthyroid
MMI & PTU:
1) Clinical improvement should begin within how long? Why?
2) Typical duration of therapy is what?
1) 4-8 weeks; Intrathyroid pool is diminished
2) 12-24 months
MMI & PTU
1) What is the goal of therapy? How likely is this to occur?
2) What should you do if a relapse occurs after therapy?
1) Goal is to induce long term remission
Average ~50% when anti-thyroid medications are used alone
2) Radioactive iodine is preferred over another course of anti-thyroid medication
Radioactive iodine I-131:
1) What is the MOA?
2) Explain how it works in more detail
1) Taken up by the thyroid & emits β ionizing particles
2) β radiation results in necrosis and destruction of the follicular cells; provokes an intense inflammatory reaction
-Stored thyroid hormones leak into the circulation from the disrupted follicles
