Mod 5 Thyroid and parathyroid glands

Question 1

What is the metabolic hormone?

Answer 1

a hormone that affects every cell

Question 2

What are the two metabolic hormones?

Answer 2

Thyroxine (T4) and triiodothyronine (T3)

Question 3

What are the differences between T4 and T3?

Answer 3

they are structurally similar but have different numbers of iodine atoms bound

Question 4

What is T4?

Answer 4

T4 is the major hormone secreted by the thyroid gland

Question 5

What is T3?

Answer 5

T3 is formed by the target tissues by the conversion from T4 and more biologically active

Question 6

Difference between amino-acid based hormones and steroid hormones?

Answer 6

both are amino acid-based hormones, but also a lipid-soluble hormone enters the target cells binding to the intracellular receptors in nucleus, initiates mRNA transcription for protein synthesis

Question 7

What are the main effects of the thyroid hormones T4 and T3 in the body?

Answer 7

1) regulating metabolic rate and body temperature
2) tissue growth and development
3) maintain blood pressure

Question 8

What is thyroid hormone synthesis?

Answer 8

• Thyroid hormone synthesis include large quantities of TH stored extracellularly - enough for 2-3 months

Question 9

What happens to the TSH?

Answer 9

TSH from the anterior pituitary binds to receptors on follicular cells

1) stored TH secreted
2) synthesis more colloid to refill follicle lumen

Question 10

What are the steps in synthesising TSH?

Answer 10

1) Thyroglobulin is synthesised and discharged into the follicle lumen
2) Iodide is trapped (active transported in)
3) iodide is oxidized to iodine
4) iodine attached to tyrosine in colloid and forming DIT and MIT
5) iondated tyrosines are linked together to form T4 and T3
6) thyroglobulin colloid is endocytosed and combined with a lysosome
7) lysosomes enzymes cleave T4 and T3 from thyroglobulin and hormones diffuse into the bloodstream

Question 11

Where does hormone synthesis occur?

Answer 11

Thyroid hormone synthesis occurs in thyroid gland follicles, extracellular and intracellular steps, thyroid hormones are formed from tyrosine amino acids and (lipid-soluble) and dietary iodine.

Question 12

How do thyroid hormones get transported and regulated?

Answer 12

Most T4 and T3 immediately bind to transport proteins, binds to target receptors but T3 - 10 times more active
More tissues have enzymes to convert T4 to T3

Question 13

How is hormone synthesis under control of the anterior pituitary?

Answer 13

stimulated by a decrease in TH blood levels, hypothalamic TRH (e.g. upon exposure to cold in infants), inhibited by the increase in TH blood levels, GHIH, dopamine, and glucocorticoids - excessively high in iodine

Question 14

ORDER?

Answer 14

stress/cold –> hypothalamus –> TRH–> anterior pituitary –> TSH –> thyroid gland –> thyroid hormone T4 and T3

Question 15

What is the hyperthyroid disorders? - interactivity cause

Answer 15

causes- primary thyroid gland defect, low dietary iodine, secondary to adequate TRH or TSH

Question 16

What are some hyperthyroid symptoms? (underactivity)

Answer 16

myxedema (mucous swelling), low metabolic rate, chilled, constipation, thick dry skin, puffy eyes, lethargy.

Question 17

Hyperthyroid? Goiter?

Answer 17

due to the primary thyroid gland defect/lack of iodine, a goiter may form ( an increase in TSH), treatment T4 thyroxine supplements

Question 18

Why is the thyroid gland & hormone important

Answer 18

it is critical for normal growth and brain development, that is why iodine supplements are recommended in pregnancy and breast feeding.

Question 19

Hyperthyroid: overactivity?

Answer 19

Grave’s disease, causes autoimmune conditions, abnormal antibodies (TSI) mimic TSH

Question 20

What are symptoms of grave’s disease?

Answer 20

increase in metabolic rate, sweating, high and irregular heartbeat, nervousness, weight loss, eyeball protude, goiter due to an increase in TSI

Question 21

What is the treatment for Grave’s disease?

Answer 21

surgery and radioactive iodine

Question 22

Thyroid gland: calcitonin hormone?

Answer 22

• calcitonin is released by parafollicular cells in response to an increase in Ca 2+ levels

Question 23

What are the causes of the calcitonin hormone?

Answer 23

basically unknown, is made into pharmacological doses- bone, used to treat paget’s disease and osteoporosis (because it inhibits bone reabsorption and release calcium) Ca2+ uptake

Question 24

Label the parathyroid gland

Answer 24

0pp

Question 25

Why are the parathyroid glands important?

Answer 25

they are important for Ca 2+ balance, Ca controls nerve impulses, muscle contractions, blood clotting and intracellular signaling. (NOTE DIAGRAM)

Question 26

Parathyroid imbalance? Excess

Answer 26

Hyperparathyroidism occurs when there is an excess of parathyroid hormone, it causes a parathyroid tumor. Ca+ leaches from bones, hypercalcemia –> depressed nervous system, abnormal reflex, weak muscle Ca salts deposit in kidneys and store (moth-eaten appearance and spontaneous fractures)

Question 27

Parathyroid deficiency?

Answer 27

Hypoparathyroidism - a deficiency in PTH, it causes parathyroid trauma or surgical removal

sym: hypocalcemia - excitable neurons and tingling, twitching muscles, can result in respiratory paralysis and death
treatments: Vitamin D –> Ca carbonate supplement and high calcium