Thyroid Hormone and Iodine

Question 1

What are the physiological actions of thyroid hormone?

Answer 1

Regulates metabolic rate according to requirements on the current environment (regulates energy production by mitochondria, oxygen consumption and heat production)
Normal nervous system development - critical in the immediate postnatal period, if absent for first 6-12 months results in permanent mental retardation
Normal linear growth and maturation of mineralized tissues, production of growth hormone and factors
Regulates sympathetic nervous system activity affecting cardiac activity, state of mind and vasodilation
Effects cardiac and skeletal muscle, motility and GI tract and metabolism of hormones, vitamins and drugs

Question 2

Who does iodine deficiency disease affect?

Answer 2

Can affect people of all ages but mostly pregnant women, foetus and neonate due to effects on the developing brain

Question 3

What test is used to screen for IDD?

Answer 3

TSH (thyroid stimulating hormone/thyrotropin stimulating hormone)

Question 4

What is the most common cause of excess iodine?

Answer 4

Iatrogenic administration of iodine

Exposure of normal healthy thyroid to excess iodine alone does not cause thyroid dysfunction but exposure to diseased thyroid to excess iodine may cause hypo- or hyperthyroidism