Endocrine cells are specially designed cells that release hormones into the bloodstream. Found in both the primary and secondary systems in the endocrine system, these cells allow different parts of the body to communicate with each other. Using hormones, the endocrine system targets specific organs and the cells in those organs and gives them instructions. Various hormones in the endocrine system control growth, metabolism, and the production of reproductive cells, among other things. Some types of endocrine cells include the pinealocytes, thyroid epithelial cells, parathyroid chief cells, and adrenal gland cells.
Most endocrine cells can be found in the glands that make up the endocrine system. The primary glands in the endocrine system are the pineal, hypothalamus and pituitary in the brain; the thyroid, parathyroids and thymus in the chest; the adrenals and pancreas in the abdomen; and the ovaries and testes. Specialized cells in each of these structures are responsible for secreting specific hormones.
In the pineal gland, special cells called pinealocytes create and release the hormone melatonin. This hormone is responsible for maintaining a sleep cycle that, in humans, corresponds to the natural cycle of day and night. The endocrine cells in the hypothalamus regulate homeostasis and send instructions to the gland directly below, the pituitary. Known as the master gland, the pituitary is comprised of mostly endocrine cells. It releases a variety of different hormones that regulate growth, sexual maturity and give instructions to the other glands in the endocrine system.
The endocrine cells in the thyroid, called thyroid epithelial cells, produce hormones that regulate metabolism. Below the thyroid, the parathyroid chief cells in the parathyroids control the concentration of calcium in the body. This system is self-regulating, meaning that the current level of calcium in the body determines whether the parathyroid releases its hormone.
A critical component of the immune system, the hormones released in the thymus are responsible for developing different types of T lymphocyte, or T cells. Though these immune cells are not a part of the endocrine system, they are housed within the thymus for a time where they are bathed in various hormones. These hormones, secreted by different cells in the thymus, instruct the T cells as to their future function.
Located above the kidneys, the cells in the adrenal gland secrete different types of steroids. These hormones are responsible for the “fight or flight” response. There are four types of endocrine cells located in clusters in the pancreas. Each of these types of cells releases a different hormone that works to control glucose and insulin levels in the blood.
There are also endocrine cells located within the male and female reproductive systems. These cells regulate the production of sperm in men and the release of ova in women. These glands also produce hormones that are responsible for creating secondary sexual characteristics at the onset of puberty.