The Thyroid gland

Question 1

Thyroid function

Answer 1

Developmental - essential for normal development, especially CNS and bone
Metabolic - essential for normal metabolism of many-body tissues

Question 2

Anatomy of the thyroid gland

Answer 2

Rich blood supply
Right and left Lobe
Pyramidal lobe

Question 3

The blood supply for the thyroid

Answer 3

Inferior thyroid artery from subclavian

Superior thyroid artery from carotid

Question 4

Histology

Answer 4

Follicular cells
Colloid (mainly thyroblobulin)
C- cell (parafollicular cell)

Question 5

Follicular cells

Answer 5

Synthesize and secrete TH

Question 6

C cells

Answer 6

Calcitonin

Question 7

What are thyroid hormones derived from?

Answer 7

Tyrosine molecules

Question 8

Thyroid hormones

Answer 8

T4: Major form released to blood, less active (prohormone)
T3: active form, converted in target cells

Question 9

How much of the thyroid hormone is bound to plasma protein?

Answer 9

99%

Question 10

What are the thyroid hormones bound to?

Answer 10

Mainly thyroid-binding globulin (~ 70%), also transthyretin (10-20%), albumin (10-20%)

Question 11

Thyroid hormone receptors

Answer 11

Belong to nuclear receptor superfamily, Ligand-activating transcription factors

Question 12

TH and receptors

Answer 12

High affinity for T3
Activation requires dimerization with another TR or retinoid X receptor (RXR)
TRs encoded by two genes: TR alpha and TR beta

Question 13

Functions of TH

Answer 13

Increase Metabolic rate
- Number and size of mitochondria, enzymes in metabolic chain, Na/K ATPase activity
- Positive inotropic and chronotropic effects
- Synergizes with sympathetic nervous system
Energy metabolism
- Partially antagonizes insulin signalling
- Gluconeogenesis, lipolysis

Question 14

Action TSH

Answer 14

Increases Iodine uptake
Stimulates other reactions involved in TH synthesis
Stimulates uptake of colloid
Induces growth of thyroid gland

Question 15

Euthyroid

Answer 15

Normal thyroid function

Question 16

Hyperthyroidism

Answer 16

TH excess
Primary: problem is thyroid gland itself
Secondary: problem is pituitary regulation

Question 17

Hypothyroidism

Answer 17

TH defiency

Question 18

Grave’s disease

Answer 18

Primary hyperthyroidism
Autoimmune
High circulating TH, low TSH
Weight loss, tachycardia, fatigue
Diffuse goiter (TSH receptor stimulation)
Opathalmopathy

Question 19

Hashimoto’s

Answer 19

Primary hypothyroidism
Autoimmune
Low circulating
Lethargy, intolerance to cold
Lack of growth and development 
Diffuse goitre