What is the endocrine system?

I speak a lot about endocrine disruption but realized I never reviewed what is the endocrine system. let’s do that in this post.

The endocrine system is a network of glands that secrete chemicals called hormones to help your body function properly. Hormones are chemical signals that help your body.

The endocrine system helps control the following systems,
  • Growth and development
  • Balance of systems
  • Metabolism
  • Reproduction
  • Response to stress

The endocrine system consists of:


The hypothalamus is the link between the endocrine and nervous systems.

The hypothalamus produces hormones that both stimulate and inhibit other endocrine glands. The hypothalmus can affect,

  • Heart rate
  • Blood pressure
  • Fluid balance (ADH)
  • Appetite and body weight (Corticotropin-releasing hormone)
  • Body fat (Growth hormone-releasing hormone or growth hormone-inhibiting hormone )
  • Immune system (CRH-Corticotropin-releasing hormone)
  • Thyroid function Thyrotropin releasing hormone (TRH):
  • Ovary function (Gonadotropin-releasing hormone (GnRH):
  • Sleep cycles (oxytocin)
  • Body temperature (oxytocin)

Pituitary Gland

The hypothalamus sends messages to the pituitary gland to help regulate other endocrine organs. The pituitary gland then produces,

Adrenocorticotropic hormone (ACTH) which stimulates the adrenal glands to produce hormones.

Thyroid-stimulating hormone (TSH) which stimulates the thyroid gland to produce hormones.

Growth hormone (GH) which helps children to grow. In adults, it helps maintain fat distribution and muscle mass.

Follicle-stimulating hormone (FSH) which works along with LH to ensure normal functioning of the ovaries and testes.

Prolactin stimulates breast milk production.

The posterior lobe does not make any hormones but releases them ADH  (regulates fluid) and oxytocin which helps regulate sleep.

what is the endocrine sysytemPineal Gland

The pineal gland is largely responsible for melatonin production. Melatonin helps regulate our body’s sleep cycle and reproductive hormones. Its secretion is the lowest in the daylight hours.


In addition to secreting enzymes that help break down food that we ingest, the pancreas helps regulate blood sugar as it produces insulin.

Thyroid gland

The thyroid helps regulate your metabolism.

The thyroid’s main role in the endocrine system is to regulate your metabolism, which is your body’s ability to break down food and convert it to energy.


Parathyroid hormone regulates the body’s calcium levels.


The thymus secretes thymosin which stimulates the development of T cells, which helps prevent disease. After puberty the thymus gland shrinks.


The adrenal gland help regulate metabolism and the immune system. The adrenals produce,

Cortisol which helps regulate metabolism and helps your body respond to stress. Cortisol also helps the body converts fats, proteins, and carbohydrates into energy.

Aldosterone (which helps control blood pressure).

Adrenaline (which helps your body react to stress). Epinephrine increases your heart rate which helps increase blood flow to the muscles and brain. It also help convert glycogen to glucose in the liver leading to an increase in blood sugar.

Norepinephrine will increase blood pressure.

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Sex hormones


Ovaries produce eggs and reproductive hormones, oestrogen and progesterone.


The testes produce sperm and testosterone. A small amount of circulating testosterone is converted into estradiol, a form of estrogen.

Testosterone decline is thought to have more of an effect lean mass and muscle size.

Estradiol decline is thought to result in increased body fat.

Both testosterone and estradiol levels are associated with libido and erectile function.

Now that we understand what the endocrine system does we can understand how endocrine disruptors can affect our body systems.

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