L26 - Thyroid function

Question 1

what is the function of the parathyroid

Answer 1

involved in blood Ca level regulation

Question 2

name the thyroid hormones and what they’re derived from

Answer 2

T3
T4
tyrosine

Question 3

what is colloid?

Answer 3

found within thyroid follicles and stores T3 & T4 (in thyroglobulin)

Question 4

where are the thyroid hormones synthesised (T3 & T4)

Answer 4

in principle cells that line thyroid follicles

Question 5

what cells are found between thyroid follicles and what are their function

Answer 5

C cells / parafollicular cells

secrete calcitonin - involved in regulation of Ca2+ levels

Question 6

what is unique about the thyroid gland?

Answer 6

only gland that contains follicles

only gland that stores its secretory products in inactive form outside the cells

Question 7

what happens to tyrosine to form T3 and T4

Answer 7

gets iodinated

Question 8

what is T3 made from

Answer 8

2x tyrosine
3 x iodine

(1x di-iodotyrosine & 1 x monoiodotyrosine)

Question 9

what is T4 made from

Answer 9

2x tyrosine
4x iodine

(2 x di-iodotyrosine)

Question 10

which thyroid hormone is the most potent

Answer 10

T3

Question 11

which thyroid hormone is the most abundant

Answer 11

T3

Question 12

where is the target receptor that T3 and T4 act on?

Answer 12

in the cell nucleus of target tissues

Question 13

what is the overall effect of thyroid hormones?

Answer 13

increase overall metabolism
increase basal rate
involved in body temp

Question 14

what is the effect of the receptor after T3/T4 have bound

Answer 14

stimulate / inhibit gene expression

Question 15

what is the effect of Thyroid hormones on muscles

Answer 15

1. increase protein breakdown
2. increase glycogenolysis

(increase [glucose])

Question 16

what is the effect of Thyroid hormones on Red blood cells

Answer 16

increases formation of RBCs

Question 17

what is the effect of Thyroid hormones on liver

Answer 17

1. increases glycogenolysis (glycogen breakdown)

2. increases gluconeogenesis

Question 18

what is the effect of Thyroid hormones in bones

Answer 18

involved in growth and maturation

Question 19

what is the effect of Thyroid hormones on heart

Answer 19

1. increase HR
2. increase contractility
   ‘——> increase CO
3. increase blood pressure

Question 20

what is the effect of Thyroid hormones on CNS

Answer 20

growth and development

Question 21

explain HPT axis

Answer 21

1. hypothalamus releases TRH to anterior pituitary
2. ap releases TSH to thyroid gland
3. TSH stimulates production of T3 & T4 by stimulating iodine uptake and colloid endocytosis

Question 22

what are the general effects of hyperthyroidism (increased levels of thyroid hormones)

Answer 22

1. increased basal metabollic rate
2. increased cardiac activity
3. weight loss - muscle wasting
4. hypertension
5. hyperglycaemia

Question 23

what are the general effects of hypothyroidism (decreased levels of thyroid hormones)

Answer 23

1. decreased basal metabollic rate
2. decreased heart activity
3. weight gain
4. slow reflexes and mental processes (CNS)

Question 24

what do T3 and T4 bind to in the blood stream

Answer 24

thyroid binding globulin (TBG)