Thyroid Hormones and Function Tests

These flashcards cover important concepts related to the anatomy, physiology, and pathology of the thyroid gland and its hormones.

What is the primary function of the thyroid gland?

The thyroid gland produces hormones that regulate the body's metabolism, impacting energy usage, growth, and development.

Where is the thyroid gland located?

The thyroid gland is located in the front of the neck, just below the Adam's apple.

What is thyroglobulin?

Thyroglobulin is a protein produced by the follicular cells of the thyroid that contains tyrosine residues and serves as a precursor for thyroid hormones.

How does iodine contribute to thyroid hormone synthesis?

Iodine is incorporated into tyrosine residues within thyroglobulin to form thyroid hormones; the synthesis involves iodine trapping, organification, and coupling.

What is the role of TSH in thyroid function?

Thyroid Stimulating Hormone (TSH) stimulates the thyroid gland to produce and release T3 and T4 hormones.

What are the primary thyroid hormones?

The primary thyroid hormones are Triiodothyronine (T3) and Thyroxine (T4).

How does the hypothalamic-pituitary-thyroid axis regulate thyroid hormone production?

The hypothalamus secretes TRH, stimulating the anterior pituitary to release TSH, which then stimulates the thyroid gland to produce T3 and T4.

What is the significance of negative feedback in thyroid hormone regulation?

Increased levels of thyroid hormones (T3/T4) inhibit TSH secretion from the pituitary, maintaining hormonal balance.

What is hyperthyroidism?

Hyperthyroidism is a metabolic state caused by an excess of circulating active thyroid hormone, leading to increased metabolism.

What is the classic triad of symptoms in hyperthyroidism?

The classic triad of symptoms in hyperthyroidism includes increased serum T3 and T4, goiter, and Graves' ophthalmopathy (bulging eyes).

What laboratory test is used to confirm hypothyroidism?

A Thyroid Stimulating Hormone (TSH) test is used to confirm hypothyroidism; elevated TSH levels indicate an underactive thyroid.

What is the difference between primary and secondary hypothyroidism?

Primary hypothyroidism originates from the thyroid gland itself, while secondary hypothyroidism is due to insufficient TSH production by the pituitary gland.

What is the function of calcitonin?

Calcitonin is produced by parafollicular cells of the thyroid and helps regulate calcium and phosphorus metabolism.

What dietary source is primarily responsible for iodine intake?

Dietary iodine is primarily obtained from seafood and iodized salt.

In what scenario may 'thyroid storm' occur?

Thyroid storm may occur in patients with thyrotoxicosis due to extreme stressors like infection or childbirth.

What are the main types of thyroid carcinoma?

The main types of thyroid carcinoma are Papillary, Follicular, Medullary, and Undifferentiated thyroid carcinoma.

What is the role of antibodies in autoimmune thyroid diseases?

Autoantibodies play a critical role by either stimulating thyroid hormone production (as in Graves' disease) or destroying thyroid tissue (as in Hashimoto thyroiditis).