Lecture 20 Flashcards
Describe the structure of the thyroid hormone and location of the thyroid gland
The thyroid gland sits in the neck surrounding the trachea
It has two lobes joined by the isthmus
The hormone consists of two linked tyrosine residues with iodine at 3 (T3) or 4 (T4) positions on the aromatic rings
What are the names of the thyroid hormone precursors and where are they formed?
Monoiodotyrosine (MIT) and diiodotyrosine (DIT) are formed by iodination of thyroglobulin tyrosine residues
What is the name of the hormone that stimulates the anterior pituitary gland to release thyroid stimulating hormone?
Thyrotopin-releasing hormone (TRH) from the hypothalamus
Which receptors does thyroid stimulating hormone bind to?
The TSH receptors are G-protein coupled receptors that stimulate the production of cAMP (i.e. Gs linked) leading to the activation of protein kinase A (PKA).
What are the three main functional domains that thyroid receptors consist of
DNA binding domain
transactivation domain at the amino terminus interacts with other transcription factors to repress or activate transcription
A thyroid hormone-binding and dimerization domain at the carboxy-terminus
What are some of the functions of the thyroid hormone?
Stimulate basal metabolic rate
Increase heat production by increasing number of mitochondria
Stimulating metabolic pathways
Increasing cells responses to catecholamines
Disease resulting from malfunction of thyroid hormone synthesis/secretion
Can arise from deficiency is thyroid hormone or too much thyroid hormone.
What are some of the diseases
Cretinism (Dwarfed stature, Mental deficiency, Poor bone development, Slow pulse, Muscle weakness and GI disturbances).
myxedema (Thick puffy skin, Muscle weakness, Slow speech, Mental deterioration, Intolerance to cold)
Hashimoto’s disease - results in destruction of thyroid follicles from production of an antibody that blocks the TSH receptor
Graves disease- caused by the production of thyroid stimulating immunoglobulin
