Lecture 21: Thyroid Hormones Flashcards
What is the mechanism of the Iodide pump?
Sodium/Iodide symporter (2:1) in basal membrane of thyroid cell via Na/K ATPase pump
How is iodide transported across the apical membrane into the follicle of a cell?
Pendrin = Chloride-iodide counter-transporter
How are thyroid hormones synthesized?
Iodine combines with tyrosine or thyroglobulin (catalyzed by peroxidase); resulting in MIT, DIT which make thyroxine or triiodothyronine
What is the major hormonal product when synthesizing thyroid hormones from iodine?
Thyroxine (T4)
What is the most notable function of thyroid hormones?
Increased cellular metabolic activity
What is the relationship between BMR and thyroid hormone levels?
BMR decreases drastically during hypothyroidism; gradually increases during hyperthyroidism
What are the causes of hyperthyroidism?
Grave’s disease, adenoma
Describe Grave’s disease
High concentrations of circulating thyroid-stimulating immunoglobulins - mimic TSH and bind to TSH receptors, resulting in high thyroxine levels and low TSH levels; no negative feedback
What are the symptoms of hyperthyroidism?
Excitability, sweating, weight loss, muscle weakness, diarrhea, nervousness, inability to sleep, hand tremor, exopthalmos
What treatment is recommended for individuals with hyperthyroidism?
Removal of some of the thyroid gland, radioactive iodine
What are some causes of hypothyroidism?
Hashimoto disease, endemic goiter, cretinism
What are symptoms of hypothyroidism?
Lethargy, weight gain, excessive sleeping, myxedema, atherosclerosis
What treatment is recommended for individuals with hypothyroidism?
Oral medication
Which anti-thyroid drug inhibits iodine uptake by inhibiting I-/Na+ co-transporter?
Thiocyanate ions
Which anti-thyroid drug inhibits the action of peroxidase and is used to treat hyperthyroidism?
Propylthiouracil
