Endo Thyroid Quiz

The thyroid requires a good supply of what from the diet to function correctly?

Iodine

How much iodine is required in a person’s lifetime?

Teaspoon

What is the Wolff-Khaikoff effect?

reduction of thyroid hormone levels caused by ingestion of a large amount of iodine

In the Wolff-Khaikoff effect, how much iodine is consumed?

Large amount

What demographic is advised to take 50% more iodine ?

Pregnant women

T/F: High iodine levels can induce both hypo or hyperthyroidism.

True

What is the name of a non-cancerous, abnormal enlargement of the thyroid gland?

Goiter

Are goiters more common in men or women?

Women

What are the causes of goiters?

Iodine excess OR deficiency

What is the result of an iodine deficiency?

Thyroxine levels go down

TSH levels go up

What can an iodine excess cause?

Symptoms like iodine deficiency goiter

What is the term for something that interferes with the body’s use of iodine?

Goitrogen

What is sometimes suggested for those with hypothyroidism?

Decrease gluten intake so that anti-thyroid antibodies decrease

T/F: Halogens block iodine receptors and can lower iodine in the body.

True

Where is T4 converted to T3?

Liver and gut

Which of D1 and D2 is extracellular? Intracellular?

D1 - extracellular

D2 - intracellular

What enzyme is responsible for converting T4 to T3 by removing one atom of I2?

5’ deiodinase

At what position is an I2 removed to produce T3 from T4?

5’ position

What can the target tissues also convert T4 to besides T3?

Reverse T3

What is the effect of reverse T3?

occupies T3 receptors

does NOT activate the receptor

blocks T3 effects

In what situation is reverse T3 produced?

Stress, chronic illness, chronic fatigue, surgery, diabetes, heart disease, starvation, organ disease

What kind of hormones are T4 and T3?

Amine hormones

How do T3 and T4 act?

Lipophilic

When circulating, what are T3 and T4 bound to?

Thyroxine-binding globulin

Which thyroid hormones are physiologically active?

Free thyroid hormones

What is the role of thyroxine-binding globulin (TBG)?

Provide large reservoir of circulating thyroid hormones

T/F: Thyroid hormones act on virtually every organ system in the human body.

True

Which hormones are known as metabolic hormones?

Thyroid hormones

What is the result of an increased basal metabolic rate?

Increased oxygen consumption and body temperature

Thyroid hormones increase oxygen consumption in all tissues EXCEPT?

Brain, gonads, and spleen

How do thyroid hormones increase oxygen consumption?

Increase synthesis and activity of Na+-K+ ATPase

T/F: Thyroid hormones increase Na+-K+ ATPase activity, oxygen consumption, BMR, and heat production.

True

What does increased oxygen consumption depend on?

Increased availability of substrates for oxidative metabolism

How do thyroid hormones affect glucose absorption?

Increase glucose absorption

What is the overall effect of thyroid hormones?

Catabolic

T/F: Thyroid hormones increase protein degradation only.

False - increase protein synthesis as well

What happens to muscle mass with thyroid hormones?

Muscle mass decreases

What is thyroid hormone required for?

Growth to adult size

Thyroid hormones act synergistically with what to promote bone formation?

Growth hormone and somatomedins/IGFs

What do thyroid hormones promote relating to bone?

Ossification and fusion of bone plates

Bone maturation

In hyperthyroidism, bone age is less than chronologic age.

False - hyPOthyroidism!