Question 1

Which of the following best describes the chemical structure of thyroid hormones T3 and T4?

Accepted Answer

They are composed of the amino acid tyrosine with attached iodine atoms.

Question 2

A patient presents with fatigue, weight gain, and cold intolerance. Laboratory tests reveal low levels of T3 and T4. Which of the following is the most likely diagnosis?

Accepted Answer

Hypothyroidism

Question 3

Which hormone is released by the hypothalamus to stimulate the anterior pituitary in the thyroid hormone axis?

Accepted Answer

TRH (Thyroid Releasing Hormone)

Question 4

What is the primary function of T3 at the cellular level?

Accepted Answer

It binds to intracellular receptors and alters gene expression.

Question 5

Which of the following best explains why T3 is considered the 'active' thyroid hormone?

Accepted Answer

T3 has a higher affinity for thyroid hormone receptors and greater biological activity than T4.

Question 6

A child with low T3 levels is most likely to experience which of the following?

Accepted Answer

Growth retardation and delayed development

Question 7

Which process is increased by T3 to raise blood glucose levels?

Accepted Answer

Gluconeogenesis and glycogenolysis

Question 8

A patient develops a goiter due to iodine deficiency. Which step in thyroid hormone synthesis is directly affected?

Accepted Answer

Attachment of iodine atoms to tyrosine residues

Question 9

Which of the following symptoms is most characteristic of hyperthyroidism?

Accepted Answer

Weight loss and rapid heart rate

Question 10

In the regulation of thyroid hormone, which sequence correctly describes the hormonal cascade?

Accepted Answer

Hypothalamus releases TRH $$\rightarrow$$ Anterior pituitary releases TSH $$\rightarrow$$ Thyroid releases T3 and T4

Question 11

Which of the following is a direct effect of T3 on lipid metabolism?

Accepted Answer

Increased lipolysis and reduced cholesterol in blood

Question 12

A researcher studies tadpoles deprived of thyroid hormone. What developmental process will be most affected?

Accepted Answer

Morphogenesis

Question 13

Which disease is associated with antibodies activating thyroid hormone production, leading to excess thyroid hormone?

Accepted Answer

Grave's Disease

Question 14

A person eats burgers containing thyroid tissue and develops symptoms of thyrotoxicosis. What is the most likely explanation?

Accepted Answer

Ingestion of exogenous thyroid hormone from the meat

Question 15

Which of the following equations best represents the conversion of T4 to T3 in peripheral tissues?

Accepted Answer

$$T_4$$ \xrightarrow{deiodinase} $$T_3$$

Question 16

Which of the following is a consequence of congenital hypothyroidism (cretinism) in humans?

Accepted Answer

Significant impairment of brain and spinal cord development

Question 17

If a patient has elevated TSH but low T3 and T4, which condition is most likely?

Accepted Answer

Primary hypothyroidism

Question 18

Which of the following best describes the role of T3 in skeletal muscle?

Accepted Answer

It increases myosin protein expression, enhancing muscle contraction.

Question 19

Which of the following symptoms is most likely in a patient with excess thyroid hormone?

Accepted Answer

Diarrhea, rapid heart rate, and weight loss

Question 20

Which of the following is a plausible multi-step effect of T3 on metabolism?

Accepted Answer

T3 binds to nuclear receptors $$\rightarrow$$ alters gene expression $$\rightarrow$$ increases enzymes for gluconeogenesis $$\rightarrow$$ raises blood glucose

Thyroid Hormone: Structure, Function, and Clinical Relevance

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