human endocrine system: Quick Facts

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The principal glands of the female and male human endocrine systems.

Bernard, Claude

Addison, Thomas

Neurohormones are released from neurosecretory nerve cells. These nerve cells are considered true endocrine cells because they produce and secrete hormones that enter the circulation to reach their target cells.

Diagram showing the relationships among vertebrate endocrine glands, including the pituitary-hypothalamus system, pituitary hormones and their endocrine targets, and feedback loops. Arrows connect the hypothalamus and pituitary to glands such as the thyroid, ovary, testis, adrenal cortex, adrenal medulla, parathyroid, ultimobranchial gland, gastrointestinal organs, and pancreas, with major hormones labeled for each gland.

Diagram of the menstrual cycle showing hormone levels, follicle development, and endometrial changes across 28 days. It highlights menstruation, ovulation, and the follicular and luteal phases, with labeled curves for estrogen, progesterone, FSH, and LH.

Diagram of a typical endocrine cell showing labeled internal structures, including the nucleus, endoplasmic reticulum, Golgi apparatus, cytoplasm, and secretory granules, with arrows illustrating the pathway of hormone synthesis and exocytosis.

Diagram showing a cross-section of a pancreatic islet of Langerhans on the left, with alpha, beta, and delta cells labeled by color, and on the right, arrows illustrating paracrine interactions among these cell types through hormones glucagon, insulin, and somatostatin.

Major glands of the human endocrine system. The hypothalamus stimulates the pituitary gland and influences food intake, weight regulation, fluid intake and balance, thirst, body heat, and the sleep cycle. Pituitary hormones stimulate growth, egg and sperm development, milk secretion, and release of hormones by other glands. The pineal gland may play a significant role in sexual maturation and the circadian rhythm. Thyroid hormones regulate the metabolic rate of tissues, stimulate the contraction of heart muscle, and are necessary for normal growth and brain development before birth and during infancy. Parathyroid hormone regulates calcium, phosphorus, and magnesium levels. The adrenal glands regulate salt and water retention, some reactions of the immune system, and blood pressure. The islets of Langerhans regulate blood sugar levels. The ovaries and testes produce hormones that regulate the reproductive system and that produce male and female secondary sex characteristics.

parafollicular cell; thyroid gland

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Hormone adrenal gland ovary thyroid gland pancreas pituitary gland hypothalamus testis pineal gland thymus human nervous system human eye human digestive system human respiratory system renal system human cardiovascular system human sensory reception human reproductive system human skin human skeleton

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