Thyroid Drugs Flashcards
Biosynthesis of Thyroid Hormones
A. Uptake
Active transport via Na+/I symporter
B. Oxidation
Iodide to Iodine
C. Organification
Iodination of tyrosine residues of Tg
I2 + TG → MIT + DIT
D. Coupling
MIT + DIT = T3
DIT + DIT = T4
E. Proteolytic Release
Thyroglobulin reenters tue follicular cell bby endocytosis and undergoes proteolysis
F. Peripheral Conversion of T4 to T3
Hypothyroidism
Low T4, High TSH
Bradycardia
Weight Gain
Cold Intolerance
Constipation
Memory Loss
Lethargy
Disorders associated with Hypothyroidism
- Infantile Hypothyroidism
- Myxedema
- Hashimoto’s Disease
Hyperthyroidism
High T4, Low TSH
Diarrhea
Heat intolerance
Exophthalmos
Insomnia
weight Loss
Tachycardia
Disease associated with Hyperthroidism
Grave’s Disease
Thyrotoxicosis
Thyroid Storm
Drugs for Hypothyroidism
Levo-T4 (Levo-Thyroxine)
Levo-T3(Levo-Thyronine)
Liotrix T4/T3
1st line drug for hypothyroidism
Levo-T4 (Levo-Thyroxine)
1st line in myxedema coma
Levo-T3 (Levo-Thyronine)
MOA of Anti-hypothyroidism
Activation of nuclear receptors results in gene expression with RNA formulation and protein synthesis
Drugs for Hyperthyroidism
Thionamides
* PTU- propylthiuracil
* Methimazole
* Carbimazole
Inorganic Anions
* Perchlorate
* Thiocyanate
Iodide Salts
* SSKI (saturated solution of Potassium Iodide)
* Lugol’s Solution (strong Iodine Solution) 5% I2 (KI)
* Radioactive iodine - Sodium Iodide (I-131)
Radiocontrast dyes
* Ipodate, Iopanoic acid
Dexametasone
Beta Blocker
*Propanolo(Inderal®)
1st line drugs for hyperthyroidism
Thionamides
MOA of Thioamide Drugs
Inhibit thyroid peroxidase (TPO) reactions & the coupling of Iodotyrosine
Antihyperthyroidism drug safe for Pregnant
PTU- propylthiuracil
Side Effects of Thioamide Drugs
Agranulocytosis : Dec, Granulocyte, Inc. Risk Of Infection (Fever, Sorethroat, Oral Ulcers)
PTU
Rapid onset
Shorter duration of action
Thyroid storm
10x PTU dose of methimazole
SE: Hepatitis, Rash, Agranulocytosis
Methimazole
Slow onset
Longer duration of action
Maintenance
10x more potent
SE: Obstructive jaundice (icterus), Teratogenic
DOC in amoiodarone-induces hyperthyroidism
Perchlorate
MOA of Inorganic Anions
inhibit iodides uptake (compete with iodide transport into cells)
MOA of Iodide Salts
Inhibit iodine organification and hormone release; Inducing Wolff-chaikoff Effect
Initial Manangement of Thyroid storm; Preoperative control of hyperthyroidism
Iodides
* Lugol’s Solution
* KISS
Contraindications for Iodides
Pregnant - lead to fetal goiter Breatfeeding (lactation) - lead to goiter
MOA of Radioactive Iodine
Emits B-particles that destroys thyroid tissues
CI to Radioactive Iodine (Na Iodide I-131)
Pregnancy
Breastfeeding
Inhibit the peripheral conversion of T4T3
Dexamethasone
Widely used in treatment of Thyrotoxicosis and Thyroid Storm
Beta Blocker: Propanolol (Inderal®)
