Thyroid Gland

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Which protein has the shortest half-life among TBG, transthyretin, and albumin?

They all have the same half-life

TBG

Transthyretin (correct)

Albumin

What percentage of the circulating T4 is normally converted to RT3?

5%

13%

45% (correct)

87%

Which protein binds most of the circulating T4 under physiologic conditions?

None of the proteins bind T4 significantly

TBG (correct)

Albumin

Transthyretin

What percentage of circulating T3 is secreted by the thyroid gland?

13% Signup and view all the answers

What is the primary function of the thyroid gland?

Secreting thyroid hormones to maintain metabolism levels Signup and view all the answers

What can be a cause of hypothyroidism due to pituitary failure?

Fetal hypopituitary hypothyroidism Signup and view all the answers

How does iodine deficiency lead to goiter formation?

By causing thyroid hypertrophy Signup and view all the answers

How can hypothyroidism in adults be characterized?

Poor resistance to cold and slowed mental and physical functions Signup and view all the answers

Which condition can drugs cause by interfering with the iodide-trapping mechanism?

Thyroid hormone synthesis Signup and view all the answers

What are the consequences of thyroid gland dysfunction during fetal and neonatal life?

Severe mental retardation and dwarfism Signup and view all the answers

What substance can paradoxically inhibit thyroid function under certain conditions?

Iodide Signup and view all the answers

How is thyroid function regulated?

Via thyroid-stimulating hormone (TSH) from the anterior pituitary Signup and view all the answers

What is the name of the mild and transient inhibition of hormone synthesis produced by large doses of iodide on the thyroid?

Wolff-Chaikoff effect Signup and view all the answers

What are individuals called who are hypothyroid from birth or before?

Cretins Signup and view all the answers

What happens to plasma cholesterol levels in completely athyreotic adults?

Elevated Signup and view all the answers

What is one of the most common causes of preventable mental retardation worldwide?

Congenital hypothyroidism Signup and view all the answers

What is the main reason why thyroid hormones need to enter cells?

To increase metabolic rate Signup and view all the answers

Which disorder is characterized by body wasting, nervousness, and tachycardia due to an overactive thyroid gland?

Graves disease Signup and view all the answers

What critical roles do thyroid hormones play in development, especially related to the nervous system?

Aiding in normal mentation Signup and view all the answers

What can be done to address iodide deficiency as mentioned in the text?

Adding iodized salt to the diet Signup and view all the answers

What is a characteristic symptom of hyperthyroidism according to the text?

Fine tremor of the outstretched fingers Signup and view all the answers

How can congenital hypothyroidism be treated shortly after birth?

Levothyroxine administration Signup and view all the answers

What are the primary functions of the thyroid gland?

Regulate metabolism and influence body mass and mentation Signup and view all the answers

What is the recommended way to assess thyroid function according to the text?

Uptake of tracer doses of radioactive iodine Signup and view all the answers

What are the consequences of thyroid dysfunction during fetal and neonatal life?

Severe mental retardation and dwarfism Signup and view all the answers

How does excess thyroid secretion affect the body?

Results in nervousness, tachycardia, tremor, and excess heat production Signup and view all the answers

What controls thyroid function in the body?

Thyroid-stimulating hormone (TSH) from the anterior pituitary Signup and view all the answers

What symptoms are commonly observed in completely athyreotic adults?

Coarse and sparse hair, dry and yellowish skin, intolerance to cold, slow mentation Signup and view all the answers

What are the consequences of congenital hypothyroidism in children?

Dwarfism and mental retardation Signup and view all the answers

How does maternal antithyroid antibodies affect fetal thyroid function?

Cross the placenta and damage the fetal thyroid Signup and view all the answers

What is the potential outcome for children with congenital hypothyroidism if treatment is initiated promptly after birth?

Normal growth and development with avoidance of mental retardation Signup and view all the answers

What is the first product generated in the thyroid hormone synthesis process?

MIT Signup and view all the answers

Which enzyme is responsible for generating reactive iodine species that attack thyroglobulin?

Thyroid Peroxidase Signup and view all the answers

In the normal human thyroid, what is the average distribution of iodinated compounds for T4?

35% Signup and view all the answers

How is T3 formed in the thyroid gland?

Condensation of MIT with DIT Signup and view all the answers

What is the role of calcitonin in thyroid gland function?

Regulates circulating levels of thyroid hormones Signup and view all the answers

How does the thyroid gland respond to high circulating levels of thyroid hormones?

Undergoes negative feedback control Signup and view all the answers

Which enzyme is responsible for mediating the oxidation and iodide reaction in thyroglobulin?

Thyroid peroxidase Signup and view all the answers

What is the molecular weight of thyroglobulin and its carbohydrate composition?

$660 kDa, 10% carbohydrate by weight Signup and view all the answers

What happens to the thyroid gland when TSH stimulation is prolonged?

It undergoes hypertrophy. Signup and view all the answers

What is the main cause of an enlarged thyroid gland known as a goiter?

Overstimulation by TSH Signup and view all the answers

What characterizes the syndrome of adult hypothyroidism, often referred to as myxedema?

Skin changes Signup and view all the answers

What is the immediate effect after the administration of TSH in terms of thyroid activity?

Enhanced synthesis of T3 and T4 Signup and view all the answers

What is the primary mechanism by which thyroid hormones exert their effects within cells?

Interacting directly with DNA Signup and view all the answers

Which of the following best describes the consequences of hypothyroidism in neonatal life?

Mental retardation and dwarfism Signup and view all the answers

In the context of thyroid gland dysfunction, what is the primary difference between hypothyroidism and overactivity of the thyroid gland?

Hypothyroidism involves a reduction in secretion of TSH, while overactivity is triggered by autoantibodies. Signup and view all the answers