ENDO - Clinical Pharmacology of Thyroid and Anti-Thyroid Drugs Flashcards
(a) Describe thyroid structure.
(b) What do follicular cells do?
(c) What does iodine do in the context of the thyroid?
- Made up of numerous follicles that have a colloid centre encompassed by follicular cells
- Trap and secrete iodine - secrete TG
- Rapidly absorbed, co-transportedthrough active transport via Na/I symporter into the follicular cell
What are the general steps behind thyroid hormone formation?
Iodine trapping
Iodine and Tg secretion into lumen
Iodination
Conjugation
Endocytosis
Proteolysis
Secretion into circulation
Hyperplasia
(a) What exactly do follicular cells do to iodinated TG?
(b) Describe the amounts of thyroid hormone released upon formation.
(c) Why does T3 have a high efficacy?
- Take it up, hydrolyse it and release T3and T4 into the blood, these then bind to plasma proteins
- T3and rT3released in equal quantities but only T3 and T4 physiologically active
- Higher affinity of T3 for the thyroid hormone receptors
How can hypo- and hyperthyroidism affect drug metabolism?
Increased/decreased rates of metabolism which can in turn affect how much drugs are metabolised
HYPER - Increased. HYPO - Decreased
List some common causes of hyperthyroidism.
- Toxic diffuse goitre e.g Graves
- Toxic adenoma
- Toxic multinodular goitre e.g Plummer’s
- Excessive pituitary TSH or thyroid hormone ingestion
- Iodine-induced
- Silent thyroiditis e.g lymphocytic and postpartum variations
List some common causes of hypothyroidism.
- Autoimmune - Hashimoto’s
- Iatrogenic causes e.g external radiation towards neck for lymphoma or other cancers, thyroidectomy
- Iodine and TSH deficiencies
- Overexpression of type 3 deiodinase in infantile hemangioma
- Congenital causes
- Silent thyroiditis
- Withdrawal of thyroxine treatment in individuals with non-functioning thyroids
- Hypothalamic disease and hypopituitarism
