Flashcards in Thyroid gland Deck (20)
Describe the location of the thyroid gland.
Sits on the trachea,joined by isthmus
What are the dimensions and weight of the thyroid gland?
Each lobe is:
adult gland weighs 10-20g
When is the thyroid gland enlarged?
-later portion of menstrual cycle
Where does the blood supply to the thyroid gland come from?
-The thyroid gland has a rich blood supply from the external carotid and subclavian arteries via the superior and inferior thyroid arteries
Where does the thyroid gland arise from and what is it's blood flow?
external carotid artery
blood flow is 4-6ml/min/g of tissue
What are the functions of the thyroid hormones?
-neural development in foetus
-growth in the young child
Concentrates iodine for incorporation into thyroid hormones
Contains 60-65% of body iodine
What is the active unit of the thyroid gland?
A follicle( composed of follicular cells)
Which cells secrete calcitonin?
parafollicular or 'C' cells of the thyroid gland
Why is T4 converted to T3 in the periphery?
How is this conversion brought about?
T3 is more potent than T4 at thyroid receptors. T3 acts on the thyrotrophs to decrease release of TSH and to decrease release of TRH from the hypothalamus. This conversion of T4 to T3 is brought about by deiodination
What is Hashimoto's thyroditis?
-antibodies to thyroglobulin or thyroid peroxidase
hat is the function of thyroid perixidase?
In the presence of hydrogen peroxidase, it allows for organification of iodine.
What does addition of iodine to tyrosine formed? How are T3 & T4 subsequently formed
How can hypothyroidism be caused?
-radiotheraphy or surgery for hyperthyroidism
-failure of delivery of thyroid hormones in the foetus i.e cretinism
How can we treat hypothyroidism?
-T4; has a half life of 6days;effects last 14 days
-Liothyronine(sodium salt of T3) has a half life of 2-4 days,effects last 8 days
What is the dietary iodine requirement
What amount of iodine intake signifies an iodine deficiency?
substances that suppress hormone secretion, so increase TSH secretion, leading to a goitre
What causes hyperthyroidism( thyrotoxicosis)?
-GRAVES' DISEASE (diffuse toxic goitre): autoimmune disease with abnormal antibodies( TSAb(LATS)-produces prolonged stimulation of TSH receptors
What are some of the features of graves disease?
-Exophthalmos and upper lip retraction