Overview of Major Endocrine Glands and Their Functions

Pineal Gland

In the brain, near the center of the brain, within the epithalamus.

Function of Hormones (Pineal Gland)

Produces melatonin, which regulates sleep-wake cycles.

melationin (hormone)

Made in the pineal gland.

Tissues (Pineal Gland)

Composed of pinealocytes (cells that produce melatonin) and neuroglia.

Pituitary Gland

Base of the brain, in the sella turcica of the sphenoid bone.

Function of Hormones (Pituitary Gland)

Secretes hormones that regulate other endocrine glands (e.g., thyroid, adrenal, gonads). Includes growth hormone (GH), thyroid-stimulating hormone (TSH), and prolactin.

Hormone Synthesis (Pituitary Gland)

Made in the anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis).

Tissues (Pituitary Gland)

The anterior part is composed of glandular tissue, and the posterior part is composed of neural tissue.

Thyroid Gland

Front of the neck, below the Adam's apple, around the trachea.

Function of Hormones (Thyroid Gland)

Produces thyroid hormones (T3 and T4) that regulate metabolism, and calcitonin, which helps regulate calcium levels in the blood.

Hormone Synthesis (Thyroid Gland)

Thyroid hormones are synthesized in the thyroid follicles; calcitonin is made by parafollicular cells.

Tissues (Thyroid Gland)

Follicular cells (for T3 and T4) and parafollicular cells (for calcitonin).

Parathyroid Glands

Four small glands on the back of the thyroid gland.

Function of Hormones (Parathyroid Glands)

Produces parathyroid hormone (PTH), which regulates calcium and phosphate balance in the body.

PTH (hormone)

Made in the parathyroid glands.

Tissues (Parathyroid Glands)

Chief cells (secrete PTH) and oxyphil cells (function still unclear).

Adrenal Glands

Located on top of each kidney.

Function of Hormones (Adrenal Glands)

Secretes cortisol (stress hormone), aldosterone (regulates salt balance), and adrenaline (epinephrine), which are involved in the body's response to stress, metabolism, and water balance.

Hormone Synthesis (Adrenal Glands)

Cortisol, aldosterone, and epinephrine are synthesized in the adrenal cortex and medulla.

Tissues (Adrenal Glands)

The adrenal cortex (glandular tissue) and the adrenal medulla (neural tissue).

Pancreas

Behind the stomach, in the upper abdomen.

Function of Hormones (Pancreas)

Produces insulin (lowers blood sugar) and glucagon (raises blood sugar).

insulin, glucagon, somatostatin, and pancreatic polypeptide.  (hormone)

Made in the islets of Langerhans in the pancreas.

Tissues (Pancreas)

The pancreas contains both endocrine (islets of Langerhans) and exocrine tissue.

Ovaries (Female)

Located on either side of the uterus in females.

Function of Hormones (Ovaries)

Produces estrogen and progesterone, which regulate the menstrual cycle, pregnancy, and secondary sexual characteristics.

Estrogen, progesterone, small amount of androgens

Made in the ovarian follicles and corpus luteum.

Tissues (Ovaries)

Composed of germinal epithelium, theca cells, granulosa cells, and the corpus luteum.

Testes (Male)

Located in the scrotum in males.

Function of Hormones (Testes)

Produces testosterone, which is responsible for male reproductive functions and secondary sexual characteristics.

testosterone (hormone)

Made in the Leydig cells of the testes.

Tissues (Testes)

Composed of seminiferous tubules and interstitial (Leydig) cells.

Thymus

Located behind the sternum, between the lungs.

Function of Hormones (Thymus)

Produces thymosin, which plays a role in the development of T lymphocytes (immune cells).

thymosin, thymopoietin, and thymulin (hormone)

Made in the thymus gland.

Tissues (Thymus)

Made of epithelial and lymphatic tissue.

Hypothalamus

In the brain, just below the thalamus and above the pituitary gland.

Function of Hormones (Hypothalamus)

Produces releasing and inhibiting hormones (e.g., TRH, CRH, GnRH, somatostatin) that regulate the pituitary gland.

oxytocin, vasopressin, and growth hormone-releasing hormone (GHRH)

Made in the hypothalamus.

Tissues (Hypothalamus)

Primarily neurosecretory cells.