semester 2: L8: Hormones 2

Question 1

what does the thyroid gland secrete?

Answer 1

thyroxine (T4)

tri-iodothyronine (T3)

Question 2

What is calcitonin secreted by?

Answer 2

parafollicular cells

Question 3

What glands are embedded within the thyroid gland?

Answer 3

Parathyroid glands

Question 4

What is the thyroid gland anatomically?

Answer 4

Two flat lobes connected by isthmus

Question 5

What is the action of thyroid hormones?

Answer 5

metabolic rate of all cells
Temperature regulation (thermogenesis)
Growth and development
Nervous system activity

Question 6

Where does thyrotropin target?

Answer 6

hypothalamus

Question 7

Where does thyroid stimulating hormone target?

Answer 7

Anterior pituitary

Question 8

Where is thyroid hormone receptor?

Answer 8

in nuclei of most cells

Question 9

what does thyroid hormone receptor do?

Answer 9

Binds both T3 and T4

Higher affinity for T3

T4 entering cells de-iodinated to T3

Induce transcription & translation

Question 10

what is goitre caused by?

Answer 10

caused by lack of dietary iodine

Question 11

what is hypothyroidism caused by?

Answer 11

In childhood: cretinism
In adults: myxoedema –
low temperature, lethargy, weakness, obesity, bradycardia, dry skin

Treatment: thyroxine

Question 12

what is hyperthyroidism caused by?

Answer 12

In adults: high temperature, nervous, hyperactive, underweight, tachycardia, flushed moist skin
Treatment: surgery, drugs or radioiodine

Question 13

What is graves disease caused by?

Answer 13

Thyroid stimulating immunoglobulins
Produced by B cells infiltrating thyroid gland]

TSI stimulate thyroid follicle cells
via TSH receptor (mimic TSH)

Increased iodine uptake and T3&T4 production

Question 14

what is the treatment for graves disease?

Answer 14

Methimazole & propylthiouracil
         - block TH synthesis
Radioactive iodide
         - trapped in thyroid gland
         - radioactivity destroys part of the gland

Question 15

what is calcium involved in?

Answer 15

Bones and teeth
(can act as) Second messenger 
Hormone and neurotransmitter release
Blood clotting
Muscle contraction

Question 16

What is hypocalcaemia?

Answer 16

nerve and muscle excitation increased

bone weakness, cramps, tetany

Question 17

What is HYPERCALCAEMIA?

Answer 17

nerve and muscle excitation decreased
cardiac arrythmia
Lethargy, weakness, nausea

Question 18

how much calcium is is in bones?

Answer 18

99% of total body calcium

Question 19

what is an osteoid?

Answer 19

Connective tissue &collagen matrix

Question 20

what is a hydroxyapatite?

Answer 20

Crystals of calcium and phosphate

Question 21

What is osteoclasts?

Answer 21

• large multinucleate cells
  
  • secrete H+ ions and hydrolytic enzymes
    (digest osteoid) - bone resorption

Question 22

What are osteoblasts?

Answer 22

• bone forming cells

- produce new matrix which is mineralized

Question 23

What do calcium receptors on the thyroid glands detect?

Answer 23

cells detect change in extracellular calcium concentration

Question 24

What does decrease calcium lead to?

Answer 24

release of parathyroid hormone

Question 25

What does parathyroid stimulate?

Answer 25

stimulates osteoclasts to resorb bone (direct)
stimulates kidney reabsorption (direct)
stimulates intestinal uptake (indirect)
stimulates intestinal uptake (indirect) (via Vitamin D)

Question 26

How is Parathyroid hormone converted to Calcitriol?

Answer 26

2 steps:
liver - 25-hydroxylase
kidney - 1-hydroxylase (PTH)

- PTH and CALCITRIOL act together restore Ca

Question 27

What does calcitonin decrease?

Answer 27

Calcium concentration

inhibit osteoclasts reduce bone resorption

Question 28

What does increased calcium result in?

Answer 28

release of calcitonin

Question 29

What does calcitonin stimulate and inhibit?

Answer 29

autonomous control

- Stimulates osteoblasts 
- Inhibits kidney resorption
- does not play role in day-to-day control
- only when calcium very high

Question 30

What is Rickets (child) and Osteomalacia?

Answer 30

deficiency in bone mineralization

 - bones soft and easily fractured
 - children bow legged
 - vit D deficiency

Question 31

What is Osteoporosis?

Answer 31

both matrix and minerals lost

 - imbalance between bone resorpn. & formn.
 - disuse
 - women- lower bone mass & low oestrogen

Question 32

What is the treatment for osteoporosis?

Answer 32

oestrogen

 - synthetic oestrogen analogs
 - regular weight-bearing exercise & vit D

 - biphosphonates
        interfere with resorpn by osteoclasts
 - selective oestrogen receptor modulators
        compensates for low oestrogen