Do you know why every human has a different height? Do you know why every human has a different body shape?

Human has a system inside his/her body that called endocrine system. It is a system that stabilized our body. The main character of this system is hormones. It is a chemical substance produced by endocrine glands. Endocrine glands located inside our body and it doesn’t have a duct to transport the hormones. We can call it endocrine glands or ductless glands.

Central Nervous System

There are several endocrine glands inside our body. The first one is Hypothalamus. It is a part from central nervous system. It secretes Thyrotropin, Dopamine, Growth hormone, Somatostatin, Gonadotropin, Corticotropin, Oxytocin and Vasopressin. Each hormone has different effects to our body. These are the effects of those hormones that are secreted by the Hypothalamus.

  • Thyrotropin: it stimulates Thyroid and Prolactin.

    Central Nervous System

  • Dopamine: inhibit Prolactin.
  • Growth hormone (releasing hormone): stimulates Growth hormone.
  • Somatostatin: inhibit Growth hormone and Thyroid.
  • Gonadotropin: stimulates follicle and luteinizing hormone.
  • Corticotropin: stimulates Adrenocorticotropin.
  • Oxytocin: uterine contraction and lactation.
  • Vasopressin: increases water permeability in the distal convoluted tubule and collecting duct of nephrons, thus promoting water reabsorption and increasing blood volume.

Our second endocrine gland is Pineal gland. It secretes:

  • Melatonin: Antioxidant

 The third endocrine gland is Pituitary gland. It secretes:

  • Growth hormone: stimulates growth and cells reproduction.
  • Thyroid: stimulates Thyroxine and Triiodothyronine synthesis.
  • Adrenocorticotropic hormone: stimulates Corticosteroid and Androgen synthesis.
  • Beta (endorphin): inhibits perception of pain.
  • Follicle: In females, it stimulates maturation of ovarian follicles in ovary. In males, it stimulates maturation of seminiferous tubules, it stimulates Spermatogenesis and stimulates production of androgen from sertoli cells of the testes.
  • Luteinizing hormone: In females, it stimulates ovulation and stimulates formation of corpus luteum. In males, it stimulates testosterone synthesis.
  • Prolactin: stimulates milk synthesis.
  • Oxytocin: uterine contraction.
  • Vasopressin: increases water permeability in the distal convoluted tubule and collecting duct of nephrons, thus promoting water reabsorption and increasing blood volume.
  • Melanocyte: stimulates melanin synthesis.

Thyroid is our next gland. It secretes:

  • Triiodothyronine: stimulates body oxygen and energy consumption, thereby increasing the basal metabolic rate.
  • Thyroxine: stimulates body oxygen and energy consumption, thereby increasing the basal metabolic rate.
  • Calcitonin: stimulates osteoblasts and thus bone construction.

Alimentary System

Alimentary System

This is our Alimentary system that located inside our tummy. It consists of Stomach, Liver, Pancreas, Duodenum, Kidney and Adrenal glands/Adrenal medulla.

Our first gland in our Alimentary system is stomach. It secretes:

  • Gastrin: secretion of gastric acid
  • Ghrelin: stimulates appetite and secretion of growth hormone.
  • Neuropeptide: increased food intake and decreased physical activity.
  • Somatostatin: lowers rate of gastric emptying reduces smooth muscle contraction and blood flow within the intestine.
  • Histamine: stimulates gastric acid secretion.
  • Endothelin: smooth muscle contraction of stomach.

Our second gland in this system is Duodenum. It secretes:

  • Secretin: secretion of bicarbonate from liver.
  • Cholecystokinin: release of digestive enzymes from pancreas.

The third gland in our system is Liver. It secretes:

  • Insulin (like growth factor): regulate cell growth and development.
  • Angiotensinogen and angiotensin: Vasoconstriction.
  • Thrombopoietin: stimulates megakaryocytes to produce platelets.

Our fourth gland is Pancreas. It secretes:

  • Insulin: intake of glucose, glycogenesis and glycolysis in the liver and muscle from blood.
  • Glucagon: Glycogenesis and glycolysis in Liver.
  • Somatostatin: inhibit release of Insulin and Glucagon.
  • Pancreatic Polypeptide: self regulated the pancreas secretion activities and effect the hepatic glycogen levels.

Our last gland from alimentary system is Kidney. It secretes:

  • Renin: activates the rennin by producing angiotensin I of angiotensinogen
  • Erythropoietin: stimulate erythrocyte production.
  • Calcitriol: active form of vitamin D3.
  • Thrombopoietin: stimulates megakaryocytes to produce platelets.

Adrenal Gland

Adrenal gland consists of two major divisions. They are Adrenal cortex and Adrenal medulla. Adrenal cortex secretes:

  • Glucocorticoids: stimulate gluconeogenesis and inhibits protein synthesis.
  • Mineralocorticoids: stimulates active sodium reabsorption in kidney.
  • Androgens: In females, it has masculinizing effects. In males, it has relatively small effect compared to androgens from testes.

However, Adrenal medulla secretes:

  • Adrenaline: Fight-or-flight response. Boost the oxygen and glucose to the brain, dilate the pupils, Suppress immune system and suppress non-bodily processes (e.g. Digestion)
  • Noradrenaline: Fight-or-flight response. Increase skeletal muscle readiness.
  • Dopamine: increase heart rate and blood pressure.
  • Enkephalin: regulate pain.

Reproductive System

Reproductive System

Reproductive system has four main glands. Those are Ovary, Testes, Placenta (when pregnant) and Uterus (when pregnant).

In male, Testes is the only gland their reproductive system. Testes secrete:

  • Androgen: increased bone density, growth and strength.
  • Estradiol: prevent apoptosis of germ cells.
  • Inhibin: Inhibit production of FSH (Follicle-stimulating hormone)

In females, Ovary is important for reproduce new organism. Ovary secretes:

  • Progesterone: support pregnancy and increase core temperature during ovulation.
  • Androstenedione: substrate the estrogen.
  • Estrogens: promote formation of female second sex characteristic and maintain uterine growth.
  • Inhibin: Inhibit production of FSH (Follicle-stimulating hormone).

Our last two gland only work when females are pregnant. The first gland is Placenta. Placenta secretes:

  • Progesterone: inhibit onset of labor and inhibit lactation.
  • Estrogens: effects on mother similar to ovarian follicle estrogen.
  • Human chorionic gonadotropin: inhibit immune response.
  • Human placental lactogen: increase production of insulin.
  • Inhibin: suppress FSH (Follicle-stimulating hormone).

The last gland that worked when females are pregnant is Uterus. Uterus secretes:

  • Prolactin: milk production in mammary glands
  • Relaxin: unclear in humans and animals.

Calcium Regulation

Calcium Regulation

This system divided to Skin and Parathyroid glands. A human can has more than six Parathyroid glands. Parathyroid glands secrete:

  • Parathyroid hormones: – stimulates Ca2+ release from bone, thereby increasing blood Ca2+.                                                   – Inhibits PO4 reabsorptions in kidney, so more PO4 = is excreted.

The second gland is Skin. Skin secretes:

  • Calcidiol: inactive form of vitamin D3.



These other glands consist of Adipose tissue, Heart and Bone Marrow. Heart secretes:

  • Atrial-natriuretic peptide: reduce blood pressure by reducing systematic vascular resistance.
  • Brain natriuretic peptide: reduce blood pressure by reducing systematic vascular resistance but lesser degree than Atrial-natriuretic peptide.

Our second gland is Bone Marrow. Bone Marrow secretes:

  • Thrombopoietin: stimulates megakaryocytes to produce platelets.

The last gland producing hormone is Adipose tissue. Adipose tissue secretes:

  • Leptin: decrease of appetite and increase of metabolism.
  • Estrogens

That is all the main systems in our endocrine system. I hope this article will help you in studying biology and I hope you won’t stop studying biology because maybe it’s a part of your job.

Videos about Human Endocrine System:

Courtesy of Youtube

“And the actual achievements of biology are explanations in terms of mechanisms founded on physics and chemistry, which is not the same thing as explanations in terms of physics and chemistry.” – Michael Polanyi



Created by: Abram Dionisius Antory