Endocrine System Vocabulary

Comprehensive vocabulary flashcards covering basic principles, classes, interaction types, glands, and homeostatic disorders of the endocrine system.

Endocrine System

The body's second major controlling system that regulates cellular metabolism through chemical messengers called hormones.

Hormone

A long-distance chemical signal carried in the blood or lymph throughout the body.

Autocrine

A local chemical messenger that exerts its effects on the same cells that secrete it.

Paracrine

A local chemical messenger that acts locally on nearby cells other than the cell that secreted it.

Amino Acid–Based Hormones

A class of hormones composed of amino acid derivatives, peptides, and proteins that usually bind plasma-membrane receptors.

Steroids

Lipid-soluble hormones synthesized from cholesterol that enter cells and bind intracellular receptors.

Thyroid Hormone

An amino acid–based but lipid-soluble hormone that enters target cells and directly influences gene activity.

Up-Regulation

The process in which target cells form more receptors in response to low hormone levels.

Down-Regulation

The process in which target cells reduce their receptor number in response to high hormone levels.

Permissiveness

A hormone interaction where one hormone requires the presence of another hormone to exert its full effect.

Synergism

A hormone interaction in which multiple hormones produce the same or an amplified effect.

Antagonism

A hormone interaction in which one hormone opposes the action of another hormone.

Humoral Stimulus

Endocrine gland stimulation and hormone release triggered by changing blood levels of critical ions or nutrients.

Neural Stimulus

Hormone release caused by direct nerve-fiber stimulation.

Hormonal Stimulus

Hormone release produced in response to another hormone stimulating an endocrine organ.

Half-Life

The duration of time required for a hormone's blood concentration to decrease by half.

Posterior Pituitary (Neurohypophysis)

The neural tissue lobe of the pituitary gland that stores and releases hypothalamic neurohormones.

Anterior Pituitary (Adenohypophysis)

The glandular tissue lobe of the pituitary gland that synthesizes and secretes protein hormones.

Antidiuretic Hormone (ADH)

Hypothalamic neurohormone released by the posterior pituitary that causes renal water reabsorption into blood and reduces urine output.

Diabetes Insipidus

A condition caused by ADH deficiency due to hypothalamic or posterior pituitary damage, leading to polyuria and intense thirst.

SIADH

Syndrome caused by excess ADH resulting in fluid retention, low blood sodium, headache, and disorientation.

Oxytocin

Posterior pituitary hormone that stimulates uterine contractions during childbirth and triggers milk ejection via the let-down reflex.

Hypophyseal Portal System

A vascular connection between the hypothalamus and anterior pituitary used to transport releasing and inhibiting hormones.

Growth Hormone (GH)

Anterior pituitary hormone that promotes tissue growth, protein synthesis, and metabolic regulation with direct anti-insulin effects.

Thyroid-Stimulating Hormone (TSH)

Anterior pituitary hormone controlled by TRH that stimulates thyroid gland growth and thyroid hormone secretion.

Adrenocorticotropic Hormone (ACTH)

Anterior pituitary hormone controlled by CRH that stimulates the adrenal cortex to release corticosteroids.

Follicle-Stimulating Hormone (FSH)

Anterior pituitary gonadotropin that stimulates gamete production and ovarian follicle maturation.

Luteinizing Hormone (LH)

Anterior pituitary gonadotropin that triggers ovulation and stimulates gonadal hormone secretion.

Prolactin (PRL)

Anterior pituitary hormone inhibited primarily by dopamine/PIH that stimulates milk production.

Gigantism

A disorder resulting from Growth Hormone hypersecretion in childhood.

Acromegaly

A disorder resulting from Growth Hormone hypersecretion in adults.

Pituitary Dwarfism

A disorder resulting from Growth Hormone hyposecretion in childhood.

Thyroxine ($T_4$)

The major form of thyroid hormone secreted by thyroid follicles, composed of two tyrosines and four iodine atoms.

Triiodothyronine ($T_3$)

The active form of thyroid hormone composed of two tyrosines and three iodine atoms, possessing about ten times more biological activity than $T_4$.

Myxedema

A severe form of hypothyroidism in adults characterized by low metabolic rate and swelling.

Hashimoto Thyroiditis

A common autoimmune disorder causing hypothyroidism.

Endemic Goiter

Thyroid enlargement caused by a dietary iodine deficiency.

Congenital Hypothyroidism

Hypothyroidism present at birth leading to severe growth impairment and nervous-system developmental deficits.

Graves Disease

A common autoimmune cause of hyperthyroidism characterized by goiter and potential exophthalmos.

Calcitonin

Hormone produced by thyroid parafollicular C cells that acts antagonistically to PTH by inhibiting osteoclast activity at elevated doses.

Parathyroid Hormone (PTH)

The primary hormone regulating blood $\text{Ca}^{2+}$ homeostasis by raising blood $\text{Ca}^{2+}$ levels.

Hyperparathyroidism

Excess PTH secretion leading to bone softening and deformation, nervous-system depression, and kidney stones.

Hypoparathyroidism

PTH deficiency resulting in hypocalcemia, tetany, respiratory paralysis, and possible death.

Aldosterone

The primary mineralocorticoid produced by the adrenal cortex that promotes renal $\text{Na}^+$ reabsorption and $\text{K}^+$ secretion.

Cortisol

The principal glucocorticoid produced by the adrenal cortex that helps resist stress by promoting gluconeogenesis and raising blood glucose.

Addison Disease

Hyposecretion disorder of the adrenal cortex causing low glucocorticoids and aldosterone, leading to hypoglycemia, $\text{Na}^+$ loss, weight loss, and hypotension.

Cushing Disease / Syndrome

Condition caused by hypersecretion of glucocorticoids, causing impaired bone formation, immune suppression, and systemic dysfunction.

Adrenal Medulla

Inner neural tissue portion of the adrenal gland containing chromaffin cells that secrete epinephrine and norepinephrine.

Epinephrine

Adrenal medulla hormone that strongly promotes bronchodilation, increased metabolic activity, and heart rate during short-term stress.

Norepinephrine

Adrenal medulla hormone that strongly promotes peripheral vasoconstriction and increased blood pressure during short-term stress.

Glucagon

Hyperglycemic peptide hormone secreted by pancreatic alpha cells that raises blood glucose levels.

Insulin

Hypoglycemic protein hormone secreted by pancreatic beta cells that lowers blood glucose levels by driving glucose uptake into cells.

Glycogenolysis

The enzymatic breakdown of stored glycogen into glucose.

Gluconeogenesis

The synthesis of new glucose molecules from non-carbohydrate sources such as amino acids and fats.

Type 1 Diabetes

A form of diabetes mellitus characterized by inadequate insulin production and secretion.

Type 2 Diabetes

A form of diabetes mellitus characterized by reduced insulin effectiveness or target-cell insulin resistance.

Polyuria

Excessive urine output caused by unabsorbed glucose acting as an osmotic diuretic in diabetes mellitus.

Polydipsia

Excessive thirst triggered by dehydration from high urine output in diabetes mellitus.

Polyphagia

Excessive hunger resulting from cellular inability to utilize available glucose in diabetes mellitus.

Hyperinsulinism

Excessive secretion of insulin leading to severe hypoglycemia, disorientation, and potential loss of consciousness.

Melatonin

Amine hormone produced by pinealocytes from serotonin that regulates sleep-wake cycles and day-night rhythms.

Gastrin

Gastrointestinal tract hormone that stimulates hydrochloric acid ($\text{HCl}$) release in the stomach.

Leptin

Adipose tissue hormone that regulates appetite control and increases energy expenditure.

Atrial Natriuretic Peptide (ANP)

Hormone secreted by the heart that reduces blood $\text{Na}^+$ concentration, blood volume, and blood pressure.

Erythropoietin (EPO)

Hormone produced by the kidneys that signals bone marrow to increase red-blood-cell production.

Renin

Renal hormone that initiates the renin–angiotensin–aldosterone system controlling blood pressure and fluid balance.