By Joshua Bower Easter Revision 2014 J.Bower@warwick.ac.uk THYROID

What hormones does the thyroid gland produce? Thyroxine (T4) Tri-iodothyronine (T3) Calcitonin

List the SIX steps in thyroid hormone synthesis [6] Thyroglobulin synthesised from tyrosine Uptake and concentration of iodide Oxidation of iodide to iodine Iodination of thyroglobulin Coupling of 2 iodinated tyrosine molecules to form T4 or T3 Secretion

Thyroid Hormone synthesis (3) Follicular Lumen (COLLOID) Blood Thyroglobulin chain (tyrosine residues) Thyroglobulin synthesis pendrin Iodide (I-) iodine(Io) TPO NIS MIT and DIT mono-, di-iodotyrosine Conjugation MIT and DIT T3 and T4 TPO - thyroid peroxidase NIS – sodium-iodide symporter hydrolysis Secretion T3 & T4 Follicle cell

Describe the HPT axis

How do thyroid hormones travel? 70% bound to thyroxin binding globulin (70%) 30% bound to albumin TBG has higher affinity for T4 – readily available reserve

Which hormone is the active one? T4 is converted by deiodinases to T3, to bind to T3R and have an effect

List FOUR physiological actions of TH [4] Affects BMR Maturation and differentiation of bone, lung, brain etc Synapse formation Myelinogenesis Neuronal outgrowth Growth (regulated by GH, but needs T3/T4)

By what week of development does the foetus make its own T3/T4? After trimester 1, not enough TSH or T4/T3 can cross placenta

What is cretinism? Impaired physical and neurological development due to iodine deficiency during foetal or postnatal development Irreversible after first 2 years of life TSH levels tested for in heel prick test

List THREE signs/symptoms of hyperthyroidism [3]

What would the blood test results show in hyperthyroidism? Inc’d T3/T4 Inc’d TSH (if fault in or above pituitary gland) Dec’d TSH (if fault with thyroid gland)

What is Grave’s disease? Auto-antibody (TSI) for the TSH receptor Causes hyperthyroidism Causes goitre as TSI is stimulating thyroid gland, even if TSH levels low

List THREE signs/symptoms of hypothyroidism [3] Slow Lethargic Overweight/obese Alopecia Goitre

What would the blood test results show in hypothyroidism? Dec’d T3/T4 Inc’d TSH (usually)

List THREE possible treatments for thyroid issues [3] Drugs (inhibit production or replace hormone) Radioactive iodine (131I) to destroy gland Surgery

List THREE complications associated with thyroid gland surgery [3] General surgery issues Vocal cord nerve damage Bleeding Parathyroid gland damage

By Joshua Bower Easter Revision 2014 J.Bower@warwick.ac.uk QUESTIONS?