Thyroid/Antithyroid Drugs Flashcards
What drugs are in the Thyroid Preparatios category?
Levoxythyroxine T4
LiothyroxineT3
Liotrix mix T3, T4
What are the steps of biosynthesis of TH?
Iodine uptake into Thyroid gland
Peroxide Mediated Ox of Iodide to Iodine
Iodination of Tyrosine (MIT, DIT)
Molecules of MIT and DIT are combined to form thyroid hormones
What is combined to form T3 and T4?
MIT + DIT =T3
DIT + DIT =T4
How are T hormones secreted?
Tgb is taken up by Thy cell.
Degradation of Tgb releases thy hormone
5:1 ratio of T4:T3
What form is thy hormone transported in?
Bound to Thyroxine binding globulin
What is the mechanism of Thyroid hormine(present)?
Hormone transported into the cell. T3 binds directly to Monomer of TR while T4 needs to be converted to T3 by 5’- DEIODINASE(5DI)
What is the mechanism of Thyroid hormine(absent)?
Homo-dimerof receptor is bound to TRE.
How is secretion of TH regulated?
TRH promotes release of TSH. TSH promotes release of T3 + T4. Decreased by negative feedback at Hyp and Pit.
High Iodide inhibits. low iodide promotes
What are the physiological effects of Thyroid hormone?
SNS- Inc Beta, Dec alpha Growith- Inc Therm- Inc RepGI- pro Skin/Hair- growth Edema Cardio- Inc HR Metabolic- Inc BMR
What are the effects of Hyper/Hypothyroidism on the body?
SNS- Inc Beta adr, Dec alpha adr Growith- Inc Therm- Inc RepGI- pro Skin/Hair- growth Edema Cardio- Inc HR Metabolic- Inc BMR
What are the Type 1 causes of HypoT?
Congenital (cretinism)
Autoimmune thyroiditis (hashimotos)
Iodine Deficiency
Other: Surg, rad, meds
What are the Type 2 causes of HypoT?
Impaired TSH production
What is the Tx of Hypothyroidism?
Hormone replacement with Thyroid hormone. Levoxythyroxine -more stable -low cost -easy lab measurement -7 day HL -yeilds T3-T4
What are the adverse effects of Thyroid Hormone?`
Hyper thyroidism
Child: restlessness, insomnia, accelerated bone maturation
Adult: Nervousness, heat intolerance, heart palp, wt loss
Geriatric: atrial fib, osteoporosis
What are the differenced between Levothyroxine(T4) and Liothyronine(T3)?
T4 longer T1/2
T3 more potent
What are the causes of Primary Hyperthyroidism?
Graves disease Thyroid adenoma Autoimmune thyroiditis (hashimotos) Thyroid Storm (fatal!) Excess Iodide (usually accompanies underlying thyr. Disease)
What are the causes of Secondary Hyperthyroidism?
Dysfunction of Hypothalamus or pituitary.
What are the treatments of Hyperthyroidism?
Methimazole
Propylthiouricil
What are the Adverse effects of Methimazole and PTU?
Can cross the Placenta
Can cause a fatal hepatitis. (PTU not for someone with altered Liver funct.
Methimazole? Altered taste and smell
What antithyroid med is better for Pregnant females? THyroid storm?
PTU because it is protein bound
What are the Iodide drugs used for Antithyroid?
Potassium Iodide
Lugol’s Solution
What is the MOA of Thioamines?
Inhibits Peroxidase Reaction, Iodine organification, and coupling of iodotyrosines
Waht is the MOA of Iodides?
Inhibits hormone release by inhibiting proteolysis of Tgb.
What are the uses of Iodides?
Only inhibits for 2-8 weeks.
Good as a pre surgery drug because it decreases vascularity, size and fragility of the hyperplastic gland.
What are the Adverse effects of Iodides
Non-specific. Don’t feel good.
What is the MOA of Radiocative Iodine?
B rays destroy parenchymal cells of the tyroid
Gamma rays pass through tissue to detect conc. of RAI remaining in Thyroid
Waht are the Anion Inhibitors
Perchlorate
Pertechnetate
Thiocyanate
How can effects of Anion inhibitors be counteracted?
Large dose of Iodide
What are the Adverse effefts of Anion Inhibitors?
Perchlorate can cause aplastic Anemia
Waht are the key adjuncts of Thyroid Tx?
Propanolol Atenolol Metoprolol Diltiazem Barbiturates Bile acid sequestrants