thyroid gland

Question 1

is the thyroid gland the largest endocrine gland

Answer 1

yes

Question 2

where is the thyroid gland located

Answer 2

in the anterior neck ( 2 lateral lobes connected by the isthmus)

Question 3

what does the parathyroid gland do

Answer 3

Increases plasma Ca2+/PO4-

Stimulates bone osteoclasts

Increases kidney reabsorption

Enhances GI absorption

Question 4

what is hypoparathyroidism cause

Answer 4

Autoimmune
Accidental removal (thyroid surgery)

Question 5

symptoms of hypoparathyroidism

Answer 5

due to hypocalcaemia
Rickets – children
Osteomalacia - adults
Tingling/burning in fingertips/toes/lips
Twitchy muscles

Question 6

treatments of hypoparathyroidism

Answer 6

Vitamin D3 (cholecalciferol)
Sunlight
Natpara (synthetic PTH)

Question 7

symptoms of hyperparathyroidism

Answer 7

neurological (tiredness, depression)

osteoporosis

Question 8

what is in the thyroid gland

Answer 8

follicles, colloid, parafollicular

Question 9

what do follicular cells do

Answer 9

Composed of follicles with follicular cells that produce the glycoprotein thyroglobulin

Question 10

what does colloid do

Answer 10

containing (thyroglobulin) fills the lumen of the follicles and stores the hormones

Question 11

what do parafollicular cells

Answer 11

(C cells), produce the hormone calcitonin

Question 12

how is calcitonin released

Answer 12

The release is regulated by calcium concentration in the blood (a negative feedback mechanism operates).

Question 13

actions of calcitonin

Answer 13

Calcitonin targets the skeleton, where it:

1. Inhibits osteoclast activity (and thus bone resorption) and release calcium from the bone matrix
   Stimulates calcium uptake and incorporation into the bone matrix
2. Reduces calcium absorption from the intestine
3. Increase calcium excretion by the kidneys.

Question 14

what do follicular cells do

Answer 14

Produce the colloid of each follicle.

Produce the thyroglobulin.

Synthesise the hormones (T3 & T4) on the thyroglobulin.

Question 15

effects of thyroid hormone

Answer 15

increased metabolic rate, critical for growth/maturation and increased reactivity of the nervous system

Question 16

increased metabolic rate from thyroid hormone

Answer 16

Increased heat production

Increased delivery of oxygen and substrates

Question 17

critical for growth/maturation

Answer 17

Fetus needs hypothal/pituitary/thyroid from 12 weeks

Needed for fetal development of CNS and skeleton

Question 18

increased reactivity of the nervous system from thyroid hormone

Answer 18

Increased blood pressure, blood flow, GI motility

Question 19

what are the secondary effects of thyroid hormone

Answer 19

increased: 
heat production
  respiration
  blood pressure (Heart rate & force, CO)
  gastrointestinal motility
  neuromuscular activity

reduced
bodyweight
sleep

Question 20

what do thyroid hormones contain

Answer 20

consist of 2 closely related iodine-containing compounds

T3 and T4

Question 21

T3 thyroid hormone

Answer 21

T3 (3,5,3’-triiodothyronine)
10% of synthesised hormones
Most active form (3-5 x T4 activity)

Question 22

T4 thyroid hormone

Answer 22

T4  (3,5,3’,5’-tetraiodothyronine)
90% of synthesised hormone
 Less active than T3
 Acts as prohormone
 Converted to T3 in some tissues
 Used clinically as thyroxine

Question 23

what are the body actions of T3

Answer 23

1. increased basal metabolic rate
   Increased oxygen consumption & heat production

Range -40% to +180% of normal

[increased ventilation, cardiac output, heat loss, substrates]
(fats & proteins to glucose)

2. growth and development 
Bone/teeth
Nervous system
Lack of T3/4 in child             cretinism
(dwarfism/mental retardation)

Question 24

what are T4 and T3 synthesised from

Answer 24

tyrosine and iodine

Question 25

what are the 4 stages of thyroid synthesis

Answer 25

1. uptake of iodine
2. oxidation to iodine by peroxidase enzyme
3. organification iodine is added to tyrosines on thyroglobulin molecule
4. coupling

Question 26

control of thyroid secretion

Answer 26

limited by the availability of iodide

secretion stimulated by thyroid-stimulating hormone
(TSH) from the pituitary.

Question 27

what are the actions of TSH

Answer 27

Stimulates the release of T3 and T4 (endocytosis from the colloid)

Stimulates the synthesis of T3 and T4
Iodide uptake
Oxidation
Organification

Stimulates growth of thyroid gland

Question 28

Hyperthyroidism causes

Answer 28

• Tumour (thyroid, pituitary, etc)

- Grave’s disease is due to antibodies against the TSH receptor. (LATS, long-acting thyroid stimulator)

Question 29

symptoms of hyperthyroidism

Answer 29

• hyperactive
  
  • tachycardia
  • hot
  • weight loss
  • exophthalmos
  • goitre

Question 30

treatment of hyperthyroidism

Answer 30

• 125Iodine
• Surgery
• thiouracil, carbimazole (block T3/T4 synthesis)

Question 31

`hypothyroidism causes

Answer 31

autoimmune, antibodies against follicular cells

Question 32

symptoms of hypothyroidism

Answer 32

• sluggish
  
  • bradycardia
  • cold
  • weight gain
  • cretinism (child)

Question 33

treatment of hypothyroidism

Answer 33

thyroxine (T4)