Endocrine System Diagram: Labeled & Blank

What is an endocrine system diagram?

An endocrine system diagram is a labeled drawing of the glands that release hormones into the blood. The standard version shows a front-facing body with the glands placed where they really sit: the hypothalamus, pituitary, and pineal in the head, the thyroid and parathyroids in the neck, the thymus in the chest, the adrenal glands and pancreas in the abdomen, and the ovaries or testes in the pelvis.

The same figure is used three ways. A labeled diagram of the endocrine system is a reference. An unlabeled or blank version with numbered lines is a worksheet. An endocrine system chart, sometimes called an endocrine system map, sets the glands beside their hormones and effects. This page makes all three, with an answer key that matches the worksheet line for line.

The major endocrine glands and where they are

• Hypothalamus: a small region at the base of the brain, above the pituitary. It is part of the brain and also the endocrine system’s control centre.
• Pituitary gland: pea-sized, hanging from the hypothalamus on a stalk and sitting in a bony pocket of the skull base (the sella turcica), roughly behind the eyes. It has an anterior and a posterior lobe.
• Pineal gland: a tiny pine-cone-shaped gland deep in the brain near its centre, behind the hypothalamus.
• Thyroid gland: butterfly-shaped, in the front of the neck below the larynx, wrapped around the windpipe.
• Parathyroid glands: usually four small glands on the back of the thyroid.
• Thymus: in the upper chest behind the breastbone, above the heart. It is large in children and shrinks after puberty.
• Adrenal glands: one on top of each kidney, each with an outer cortex and an inner medulla.
• Pancreas: behind the stomach, across the back of the upper abdomen. Its hormone-making cells are the pancreatic islets.
• Gonads: the ovaries in the female pelvis and the testes in the male scrotum.

Endocrine system chart: glands, hormones, and effects

When a diagram adds hormones, these are the standard pairings an introductory course expects. Each hormone belongs to one gland; a chart that moves one is wrong.

• Hypothalamus: releasing and inhibiting hormones that control the anterior pituitary (TRH, CRH, GnRH, GHRH, and inhibiting hormones such as somatostatin). It also makes ADH and oxytocin.
• Anterior pituitary: growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin.
• Posterior pituitary: releases ADH (antidiuretic hormone, which tells the kidneys to keep water) and oxytocin (uterine contractions in labour, milk release).
• Pineal gland: melatonin, which helps set the sleep–wake cycle.
• Thyroid gland: thyroxine (T4) and triiodothyronine (T3), which set the metabolic rate, and calcitonin, which can lower blood calcium.
• Parathyroid glands: parathyroid hormone (PTH), which raises blood calcium.
• Thymus: thymosins, which help T cells mature.
• Adrenal cortex: cortisol (stress, blood glucose) and aldosterone (sodium and water balance). Adrenal medulla: adrenaline and noradrenaline for the fight-or-flight response.
• Pancreatic islets: insulin lowers blood glucose and glucagon raises it.
• Ovaries: estrogen and progesterone. Testes: testosterone.

The hypothalamus and pituitary: the control centre

The hypothalamus and pituitary sit together at the base of the brain and control much of the rest of the system. The hypothalamus releases small amounts of releasing and inhibiting hormones into a short network of portal blood vessels that runs down the pituitary stalk to the anterior pituitary. In response, the anterior pituitary releases its own hormones into the general circulation. Three of them, TSH, ACTH, and FSH with LH, act on other endocrine glands: the thyroid, the adrenal cortex, and the gonads.

The posterior pituitary works differently. It is an extension of the brain rather than a gland in its own right. Neurons whose cell bodies lie in the hypothalamus make ADH and oxytocin and send them down their axons through the stalk to be stored and released in the posterior lobe. A close-up diagram should show both routes: blood vessels to the anterior lobe and nerve fibres to the posterior lobe.

Reading a front-view endocrine diagram

Like every anatomical figure, a front-view endocrine diagram shows the person facing you, so their right side is on your left. That matters most for the pancreas. Its head sits in the C-shaped curve of the duodenum on the person’s right, which is your left, and its tail stretches across toward the spleen on the person’s left.

Level matters as much as side. The pituitary is roughly level with the eyes, not in the neck. The thyroid is below the larynx, not at the jaw. The thymus is behind the upper breastbone, not in the neck. The adrenal glands sit on the upper poles of the kidneys, which lie high against the back wall of the abdomen. Because the hypothalamus, pituitary, and pineal lie one behind another on the midline, a good diagram shows them in a magnified section of the brain rather than stacking them on a front view.

Inside the adrenal gland: cortex and medulla

An adrenal close-up is a common second figure, because each adrenal gland is really two glands in one. The outer cortex is built in three layers, each making a different class of steroid hormone. Under the capsule, the zona glomerulosa makes aldosterone, which tells the kidneys to keep sodium and water. The middle zona fasciculata, the thickest layer, makes cortisol, which raises blood glucose and shapes the stress response. The inner zona reticularis makes small amounts of androgens. The medulla at the centre is different tissue altogether. Its cells are modified nerve cells of the sympathetic nervous system, and they release adrenaline and noradrenaline within seconds of a nerve signal. A diagram of the gland should show the cortex as a rim around the medulla, with the three zones in that order from the outside in.

Three kinds of hormone

More detailed charts group hormones by their chemistry, because that decides how they reach their target.

• Steroid hormones are made from cholesterol: cortisol, aldosterone, estrogen, progesterone, and testosterone. They are fat-soluble, pass through cell membranes, and act on receptors inside the cell, often switching genes on or off.
• Peptide and protein hormones are chains of amino acids: insulin, glucagon, growth hormone, ADH, oxytocin, and the pituitary hormones. They cannot cross the membrane, so they bind receptors on the cell surface and act through second messengers inside it.
• Amine hormones are made from a single amino acid: adrenaline and noradrenaline, melatonin, and the thyroid hormones T4 and T3. The thyroid hormones are the exception in their group, because they enter cells and act on receptors inside, like steroids.

Labels by level

• Middle school: about seven glands with no hormones, such as pituitary, thyroid, thymus, adrenal glands, pancreas, and ovaries or testes.
• High school: the ten standard glands, adding the hypothalamus, pineal gland, and parathyroids.
• College: the ten glands with their main hormones written under each name, plus the feedback flow chart.
• Medical: subdivisions as well as glands, such as the anterior and posterior pituitary, the thyroid follicles and parafollicular cells, the three zones of the adrenal cortex and the medulla, and the cell types of the pancreatic islets.

Organs with endocrine tissue that diagrams often leave out

Hormones are not made only by the classic glands. Many organs have endocrine cells as a second job. Introductory diagrams usually leave them out; fuller ones list them in a side panel.

• Heart: atrial natriuretic peptide, released when the atria are stretched, which helps lower blood volume.
• Kidneys: erythropoietin, which drives red blood cell production, and the active form of vitamin D. They also release renin.
• Stomach and small intestine: gastrin, secretin, and cholecystokinin, which coordinate digestion.
• Adipose tissue: leptin, which signals the body’s energy stores.
• Skin: makes a precursor of vitamin D when exposed to sunlight.
• Placenta: during pregnancy, hormones including human chorionic gonadotropin (hCG).

Feedback loops and the endocrine system flow chart

Most hormone levels are held steady by negative feedback, which is why a flow chart of the endocrine system is a common figure. The hypothalamus–pituitary–thyroid axis is the standard example. The hypothalamus releases TRH, the anterior pituitary responds with TSH, and the thyroid responds with T4 and T3. Rising T4 and T3 then inhibit both the hypothalamus and the pituitary, so less TRH and TSH are released and thyroid output falls back. The cortisol axis (CRH, ACTH, cortisol) follows the same pattern.

Blood glucose is regulated without the pituitary. After a meal, rising glucose triggers insulin from the pancreatic islets, and glucose moves into cells. Between meals, falling glucose triggers glucagon, and the liver releases glucose. Positive feedback is rarer. Oxytocin in childbirth is the textbook case: contractions push the baby against the cervix, which triggers more oxytocin and stronger contractions until birth.

Endocrine vs exocrine glands

An endocrine gland has no duct. It releases hormones into the fluid around its cells, and the blood carries them to any cell with a matching receptor. An exocrine gland releases its product through a duct onto a surface or into a cavity, like sweat onto the skin or saliva into the mouth. The pancreas does both: most of it is exocrine tissue making digestive enzymes that drain into the duodenum, with endocrine islets scattered through it. The ovaries and testes release hormones into the blood and also release eggs or sperm. That is why both appear on an endocrine diagram even though they belong to the reproductive system too.

Male and female endocrine diagrams

Apart from the gonads, the endocrine system is the same in both sexes, so a diagram has three honest options. A female figure shows the ovaries in the pelvis on either side of the uterus. A male figure shows the testes in the scrotum. A neutral figure shows the two gonads as small separate insets. The neutral version is the most reusable worksheet, because one sheet serves the whole class. What a diagram must never do is draw both ovaries and testes inside one body, a mistake image models make often enough that this page’s rules forbid it.

Using a blank endocrine system diagram in class

• Glands first, hormones second: label the glands on the blank body, then fill in a blank chart of hormones as a second step.
• Ten labels is a good size: hypothalamus, pineal, pituitary, thyroid, parathyroids, thymus, adrenals, pancreas, ovaries, and testes.
• Make the key from the same result, so the numbering on the worksheet and the answer key match exactly.
• Use the feedback flow chart for the "how" question: give students the boxes and have them draw the stimulating and inhibiting arrows.
• Word bank or not: include one for revision, leave it out for a test. It is printed in alphabetical order.

How the endocrine system changes across a lifetime

A diagram is a snapshot of one age, and a few glands change enough to matter. The thymus is largest relative to body size in childhood, when it is busiest training T cells; after puberty it shrinks and is gradually replaced by fat, so an older adult’s thymus is hard to find. Puberty begins when the hypothalamus increases its pulses of GnRH, which raises FSH and LH from the pituitary and switches on the ovaries or testes. Growth hormone output is highest in childhood and adolescence and falls with age. At menopause the ovaries stop responding and estrogen and progesterone fall, while FSH and LH rise because negative feedback is lost. If a worksheet is about a child or an older adult, say so in the description so the thymus is drawn at the right size.

Common disorders linked to each gland

• Pancreatic islets: type 1 diabetes, where the insulin-making beta cells are destroyed, and type 2 diabetes, where the body responds poorly to insulin.
• Thyroid: hypothyroidism (too little T4 and T3, with tiredness and weight gain) and hyperthyroidism (too much, with weight loss and a fast heart rate). A goitre is an enlarged thyroid, classically from iodine deficiency.
• Adrenal cortex: Addison’s disease (too little cortisol and aldosterone) and Cushing’s syndrome (too much cortisol).
• Pituitary: too much growth hormone causes gigantism in children and acromegaly in adults; too little in childhood causes short stature.
• Posterior pituitary: too little ADH causes diabetes insipidus, with large volumes of dilute urine.