L3.2 Thyroid Function and Metabolism

Question 1

what is metabolism

Answer 1

• Metabolism refers to all the chemical reactions occurring in the body (metabolism is also for specific process e.g. breakdown of glucose)
• Includes ‘external work’ (energy used by skeletal muscles to move) and ‘internal work’ (energy used to sustain life)

Question 2

what is rate of energy expenditure

Answer 2

Rate of energy expenditure referred to as ‘metabolic rate’ (usually calories/hr or kj/hr)

Question 3

Thyroid hormone is an ______, made by combining _____ and _____. It is ____, so most is transported in the blood bound to carrier proteins, with a small amount of ______ hormone in the blood.

Answer 3

Thyroid hormone is an AMINE, made by combining TYROSINE and IODINE. It is LIPOPHILIC, so most is transported in the blood bound to carrier proteins, with a small amount of FREE hormone in the blood.

Question 4

what are the abnormalities of thyroid function?

Answer 4

hypothyroidism and hyperthyroidism

Question 5

what is hypothyroidism? symptoms? in adults and neonates?

Answer 5

• Can be primary: Thyroid gland failure
• Or secondary: Deficiency of TRH or TSH; Inadequate supply of iodine
• Symptoms - decreased metabolism, poor cold tolerance, excessive weight gain, fatigue, bradycardia, weak pulse, slow reflexes and mental function, slow or slurred speech
• In adults – myxodema (‘puffy’ esp. face)
• In neonates – cretinism & dwarfism irreversible unless treated from birth

Question 6

what is hyperthyroidism? symptoms?

Answer 6

• Most common cause is Graves’ Disease: Autoimmune production of thyroid-stimulating immunoglobulin (TSI) which activates TSH-R inducing TH release
• Can also be caused by excess TRH, TSH or TH production (usually from tumour)
• Symptoms - increased metabolism, excessive sweating, increased appetite but weight loss, muscle weakness, anxiety, palpitations, goitre
• Graves’ disease may also result in exophthalmos (bulging eyes)

Question 7

an increase in an individual’s thyroid hormone is likely to cause…

a. them to have slow reflexes and slurred speech
b. bradycardia due to sympathomimetic effects
c. them to feel much colder than usual
d. an increase in their basal metabolic rate

Answer 7

D (an increase in their basal metabolic rate)