Thyroid Pharmacology Flashcards
What is the relationship between the brain and thyroid?
The brain regulates thyroid function through the hypothalamic-pituitary thyroid axis.
What are the main characteristics of T3 and T4?
T3 (Triiodothyronine) is more potent than T4 (Thyroxine) and responsible for the physiological response to thyroid hormone.
Define hypothyroidism.
Deficiency of thyroid hormones, leading to slowed body functions and negative effects on lipid panel.
What are common indicators of hypothyroidism?
Low T4 and elevated TSH levels.
What is the role of levothyroxine in hypothyroidism?
Levothyroxine is the first choice therapy for hypothyroidism, converted to T3 and acts on nuclear transcription.
What are the adverse effects of levothyroxine?
Symptoms of hyperthyroidism, potential for arrhythmia or myocardial infarction.
What drug interactions should be monitored with levothyroxine?
Antacids, cholestyramine, warfarin, enzyme inducers (rifampin, phenobarbital), and enzyme inhibitors (cimetidine, erythromycin).
Fill in the blank: The recommended daily intake of iodine is ______ mcg.
150 mcg
What are the causes of hypothyroidism?
- Hashimoto’s thyroiditis
- Drug-induced (e.g., amiodarone, lithium)
- Iodine deficiency
- Congenital factors
What is myxedema coma?
A severe form of hypothyroidism characterized by low thyroid hormone levels and may require IV levothyroxine.
What autoimmune condition is associated with hyperthyroidism?
Graves Disease
What treatments are available for hyperthyroidism?
- Thioamides (e.g., Propylthiouracil, Methimazole)
- Iodides
- Radioactive iodine (131I)
- Beta blockers
What are the adverse effects of thioamides?
- Rash
- Agranulocytosis
- Higher risk of hepatitis with PTU in pregnancy
True or False: Levothyroxine is safe for weight loss.
False
What is the effect of low thyroid hormone levels on fertility?
Low thyroid inhibits ovulation, leading to infertility.
What is the recommended approach for dosing levothyroxine?
Daily dosing on an empty stomach and monitoring levels after 6 weeks.
What is the mechanism of action of thioamides?
Inhibit thyroid-peroxidase catalyzed reactions and block iodine organification.
What are the adverse effects of iodides like Lugol’s solution?
- Rash
- Fever
- Metallic taste
- Avoid in pregnancy
Fill in the blank: T3 is bound to _______ and _______.
albumin, thyroxine-binding globulin (TBG)
What is the impact of thyroid hormones on pregnancy?
Adequate thyroxine is necessary for fetal nervous system development; low levels can lead to complications.
What is the effect of lithium on thyroid hormones?
Lithium inhibits the release of thyroid hormones.
What are the symptoms of hyperthyroidism?
Increased metabolism, weight loss, anxiety, tremors, and heat intolerance.
What are the implications of taking levothyroxine with food?
Food and antacids can alter the pH of the GI tract and affect absorption.
T or F: Amiodarone can cause hypo or hyperthyroidism
True
what are extraendocrine AEs of amiodarone
corneal deposits
smurf-skin
pulmonary fibrosis
hepatotoxicity
how does lithium inhibit release of thyroid hormones?
blocks PLC mediated signaling mechanism
T or F: levothyroxine is more potent than liothyronine?
Fasle
liothyronine has higher potency
what are CIs for liothyronine
CVD due to sympathetic stimulation
what is liothyronine most commonly used for
short term TSH supression
What are hypothyroid preges at increased risk for
preeclampsia and early labor
what monovalent ions block iodide uptake by the tyrroid?
SCN-; CLO4-
what are AEs of monovalent ions
aplastic anemia
Iodide solutions decrease hyperthyroidism by inhibiting organification, hormone release, and what else?
decreased gland vascularity
What CCB is also used for hyperthyroidism management
diltiazem
what iodine isotope is used to treat thyroid cancer
I-131
