30 Questions
What are the two separate hormones produced by the thyroid gland?
T3 and T4
How many iodine atoms are present in each molecule of T4?
Four
What is the major use of iodine in the body?
By the thyroid
Which hormones bind and transport T3 and T4?
Thyroxine-binding globulin, transthyretin, and albumin
Where are thyroid hormones synthesized and stored bound to proteins?
In the cells of the thyroid gland
What is the major derangement in iodine deficiency?
Alteration of thyroid function
What is the name of the hormone that is essential for normal thyroid function and contains iodine?
Thyroxine
What is the name of the hormone responsible for normal thyroid function and contains iodine?
Thyroid hormone
What is the name of the hormone that is responsible for the alteration of thyroid function in iodine deficiency?
Thyroid hormone
What is the name of the hormone that binds and transports T3 and T4?
Thyroxine-binding globulin, transthyretin, and albumin
What is the normal range for serum free T4?
0.7 to 2.0 ng/dL (10 to 26 pmol/L)
What is the recommended action by the US Preventive Services Task Force (USPSTF) regarding routine screening of adults for thyroid disease?
Not recommend routine screening of adults
What is the main advantage of measuring free T4 by the dialysis method?
Not affected by variations in protein binding
Which hormone is the only metabolically active fraction of T4?
Free (unbound) thyroxine
What is the normal range for serum T3?
260 to 480 pg/dL (4.0 to 7.4 pmol/L)
What percentage of T4 and T3 are unbound?
0.03% of T4 and 0.3% of T3
What is the main purpose of measuring TSH in patients with low or high normal values?
Distinguish subclinical thyroid disease from euthyroid states
What is the range of normal T4 in serum?
5.4 to 11.5 µg/dL (57 to 148 nmol/L)
What is the main advantage of measuring total T3 or T4?
Includes protein-bound and free hormone levels
What is the American Thyroid Association's recommendation regarding screening for thyroid disease in pregnant women?
Recommends screening for thyroid disease
What controls thyroid hormone secretion through a negative feedback mechanism?
TSH from the anterior pituitary gland
What term refers to normal thyroid hormone production, regulated by TRH from the hypothalamus?
Euthyroid
Which thyroid hormone is more potent and rapid in its action than T4?
T3
What does calcitonin, secreted by the thyroid gland, regulate?
Plasma calcium levels by increasing its deposition in bone
What are the consequences of congenital hypothyroidism?
Intellectual disability and stunted growth
What are the manifestations of hypothyroidism in adults?
Lethargy and slow mentation
What does hyperthyroidism lead to?
A greatly increased metabolic rate and an enlarged thyroid gland (goiter)
What is included in the diagnostic evaluation for thyroid function?
Thyroid hormone measurements, thyroid scanning, biopsy, and imaging studies
What should patients being tested for thyroid function be assessed for?
Iodine allergies and medications containing iodine
Why can shellfish allergy be confused with iodine allergy?
Due to a long-held belief, but shellfish allergy is actually due to specific proteins in the shellfish and not iodine
Study Notes
Thyroid Hormone Regulation and Function
- The thyroid gland efficiently uptakes iodide from the blood and converts it into thyroid hormones.
- Thyroid hormone secretion is controlled by TSH from the anterior pituitary gland through a negative feedback mechanism.
- Euthyroid refers to normal thyroid hormone production, regulated by TRH from the hypothalamus.
- Thyroid hormones control cellular metabolic activity, with T3 being more potent and rapid in its action than T4.
- Thyroid hormones influence cellular processes, brain development, and are essential for normal growth.
- Calcitonin, secreted by the thyroid gland, regulates plasma calcium levels by increasing its deposition in bone.
- Congenital hypothyroidism results in intellectual disability and stunted growth, while hypothyroidism in adults manifests as lethargy and slow mentation.
- Hyperthyroidism leads to a greatly increased metabolic rate and is often associated with an enlarged thyroid gland (goiter).
- Diagnostic evaluation for thyroid function includes thyroid hormone measurements, thyroid scanning, biopsy, and imaging studies.
- Patients being tested for thyroid function should be assessed for iodine allergies and medications containing iodine.
- The relationship between shellfish allergy and iodine allergy is a long-held belief, but shellfish allergy is due to specific proteins in the shellfish and not iodine.
- Select medications can interfere with accurate testing of thyroid gland function and should be documented in the patient’s electronic health record.
Test your knowledge of thyroid hormone regulation and function with this quiz. Explore the role of thyroid hormones in cellular metabolism, growth, and brain development, as well as the impact of hypo- and hyperthyroidism on the body. Delve into diagnostic evaluations and considerations for testing thyroid function.
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