Thyroid Gland: Structure, Hormones, and Disorders

Vocabulary flashcards covering thyroid gland structure, hormones, disorders, and key pathophysiology terms from the notes.

Thyroid gland

A gland located below the larynx; essential for metabolism, growth and development; consists of two lobes connected by an isthmus.

Follicular cells

Cells that secrete thyroid hormones T3 (triiodothyronine) and T4 (thyroxine).

Parafollicular (C) cells

Cells that secrete calcitonin to decrease serum calcium.

Calcitonin

Hormone from C cells that lowers serum calcium levels.

Thyroid hormones (T3 and T4)

Regulate energy metabolism; increase basal metabolic rate and heat production; promote growth and development; affect nervous system activity and heart rate.

T3 (triiodothyronine)

Active thyroid hormone; more potent than T4 and regulates metabolism.

T4 (thyroxine)

Precursor thyroid hormone; converted to T3 in tissues to exert metabolic effects.

Hyperthyroidism

Condition of excess thyroid hormone production leading to increased metabolic activity.

Graves’ disease

Most common cause of hyperthyroidism; autoimmune overstimulation of the thyroid.

Exophthalmos

Abnormal protrusion of the eyeballs due to edema behind the eyes and sympathetic stimulation.

Hypothyroidism

Deficiency of thyroid hormones (T3/T4) causing decreased metabolic rate; can be primary (e.g., iodine deficiency, Hashimoto’s) or secondary (pituitary dysfunction).

Hashimoto’s disease

Autoimmune destruction of thyroid tissue by antibodies (thyroid peroxidase and thyroglobulin) causing hypothyroidism.

Iodine deficiency

Lack of iodine essential for thyroid hormone synthesis; can cause goitre.

Goitre (goiter)

Enlarged thyroid gland; often due to increased TSH; can be non-toxic if hormone levels are normal.

Non-toxic goitre

Enlarged thyroid due to TSH stimulation without excess hormone production.

Thyroidectomy

Surgical removal of the thyroid gland.

Thyroid ablation

Destruction or removal of thyroid tissue to reduce function.

Pituitary gland

Gland that secretes TSH; pituitary dysfunction can cause secondary hypothyroidism.

Secondary hypothyroidism

Hypothyroidism caused by pituitary dysfunction reducing TSH production.

TSH (thyroid-stimulating hormone)

Pituitary hormone that stimulates thyroid hormone production; levels rise in hypothyroidism and can increase thyroid size (goitre).

Myxedema

Severe hypothyroidism with edema, puffy features, deep voice, hypoventilation, and mental slowing.

Cretinism

Congenital hypothyroidism with intellectual disability, stunted growth, and developmental abnormalities.

Autoantibodies in Hashimoto’s disease

Thyroid peroxidase (TPO) and thyroglobulin antibodies that mediate autoimmune destruction of thyroid tissue.

Bradycardia

Slow heart rate; commonly seen with hypothyroidism.

Tachycardia

Fast heart rate; commonly seen with hyperthyroidism.

Hypometabolism signs

Symptoms of hypothyroidism: cold intolerance, lower body temperature, weight gain, decreased appetite, and bradycardia.

Hypermetabolism signs

Symptoms of hyperthyroidism: sweating, heat intolerance, weight loss with increased appetite, tachycardia, nervousness, insomnia, and increased bowel movements.