The pineal gland is a small structure located in the mid-brain. The pineal produces the hormone melatonin, which helps to regulate the sleep cycles.
The thyroid gland is the largest endocrine gland in the body. Made up of two lobes that sit on either side of the larynx, the thyroid gland releases thyrozine, which increases energy metabolism and protein metabolism.
Embedded in the rear of the thyroid gland, are four tiny bodies called the parathyroid gland. The parathyroid glands are responsible for calcium metabolism, particularly the release of calcium from the bone tissues, thus increasing the amount of calcium circulating in the bloodstream.
The thymus gland is a collection of lymph tissue that lies in the center of the chest, just above the heart. This gland is critical for the development of immunity and the development of T-lymphocyte (T-cells).
The adrenal glands are located just above the kidneys. The Adrenals are made up of two separate parts that have independent functions. The inner area called the medulla releases two hormones, adrenaline and norepinephrine, which controls our fight-or-flight response. The outer portion of the adrenal gland, the adrenal cortex, secretes three types of hormones. They include: glucocordiocoids, mineralocorticoids and the sex hormones.
Islets of Langerhans
The Islets of Langerhans are specialized cells that are located in the pancreas which secrete the hormones insulin and glucagon. The correct amounts of insulin and glucagon are required to regulate blood sugar levels. Insulin is required to transport glucose (a form of simple sugar) into the cells to be used for energy.
Insulin is also used to lower the level of sugar in the blood by increasing the rate at which the liver converts glucose into glycogen for storage in fatty tissues. Glucagon, on the other hand, causes the liver to convert glycogen back to glucose and release it back into the blood stream for use by the cells for energy.
The ovaries produce two hormones estrogen and progesterone that are responsible for the stimulation and preparation of the uterus for pregnancy.
The testes produce the hormone testosterone, which is responsible for development and maintenance of primary and secondary male sexual characteristics.
While the kidneys are not typically thought of as secreting hormones, the kidneys actually do secrete two different hormonal substances:
- Renin – helps to regulate blood pressure.
- Erythropoieten – stimulates the production of red blood cells.