Thyroid Flashcards
What connects the two lobes of the thyroid?
Isthmus
What are the two endocrine cell types in the thyroid?
Follicular and parafollicular cells
What are the three hormones secreted by the thyroid?
Thyroxine, triiodothyronine, calcitonin
What does the thyroid gland regulate? (8)
Breathing, heart rate, central and peripheral nervous system, body weight, muscle strength, menstrual cycles, body temp, cholesterol levels
What element is essential for thyroid hormone synthesis?
Iodine
What thyroid component takes up iodide?
Sodium-iodide symporters in the thyrocytes
What oxidises iodide?
Thyroperoxidase (TPO)
What is iodide incorperated into after it is oxidised and what does this form?
Selected tyrosyl residues of thyroglobulin (TG), forming mono and diiodotyrosines
What are mono and diodotyrosines formed from?
Oxidised iodide and selected tyrosyl residues of thyroglobulin
What happens to mono- and diodotyrosines?
They are couples by TPO to form thyroxine (T4) and triiodothyronine
What is thyroxine formed from?
Two diiodotyrosines
What is triiodothyronine formed from?
One monodotyrosine and one diiodotyrosine
What does T3 and T4 bind to in the bloodstream?
Thyroxine-binding globulin (TBG)
What is the most active form of thyroid hormone?
Free T3 (disassociated from TBG)
Is T3 or T4 more active?
T3- ten times more active than T4
