Thyroid Gland Flashcards
Parathyroid glands?
Superior and inferior, produce parathyroid hormone for calcium metabolism
3 histological features?
Parafollicular cells, follicular cells and colloids
What happens after TSH binds to follicular cells?
Causes TPO and TG to be produced and iodide ions to be uptaken
What happens in colloid cells?
Iodination of iodide ions
I plus TG into MIT, DIT and then T3 and 4. Catalysed by TPO and H2O2.
T3 and 4 transported to follicular cells, modified by lysosomes and released into the blood
Main hormone produced?
Tetra-iodothyronine (T4), deiodinated to T3 metabolite in target tissues
How are T3 and 4 transported in the blood?
Mostly bound to plasma proteins- thryoid-binding globulin (TBG) and albumin
Actions of hormone?
Fetal growth and development
Increase in basal metabolic rate, gluconeogenesis, cardiac output, bone maturation
How is T4 regulated?
T4 inhibits TSH and TRH
Excess iodine in cells will inhibit deiodination of T4, Wolff-Chaikoff effect
Primary hypothyroidism causes?
Autoimmune diseases like Hashimotos, more common in women
Hypothyroidism symptoms and signs?
Depression and weakness Cold intolerance Weight gain Constipation Bradycardia
Levothyroxine?
Synthetic tablet of T4, usually 100 microgram dose
Hyperthyroidism causes?
Autoimmune diseases, e.g Graves’ disease where antibodies stimulated TSH receptors. Can cause exophthalmos and growth of shin tissues. Can be due to toxic nodules
Symptoms and signs of hyperthyroidism?
Heat intolerance Weight loss Myopathy Mood swings Smooth goitre
