Describe the major endocrine glands in humans and their hormones. Explain how hormones released by the pituitary, thyroid, adrenal glands, pancreas, and gonads regulate different body functions.
Endocrine glands release hormones directly into the blood. The pituitary regulates several other glands, the thyroid influences metabolism, adrenal glands help regulate stress responses, the pancreas controls blood glucose, and gonads produce hormones involved in reproduction.
The pituitary gland located at the base of the brain is the “master gland” that controls other endocrine glands and target organs. For instance, growth hormone (GH) controls growth and cell replication; thyroid-stimulating hormone (TSH) stimulates the thyroid gland to produce its own hormones; adrenocorticotropic hormone (ACTH) influences adrenal cortex; oxytocin and antidiuretic hormones (ADH) regulate uterine contractions, milk secretion, and water reabsorption in the kidneys.
The thyroid gland located at the front part of the neck produces thyroxine and triiodothyronine – hormones that increase the body’s metabolic rate, the production of energy, and regulate the growth and maturation of organs and tissues. Adrenal glands are located above the kidneys and consist of two parts – adrenal cortex and adrenal medulla. The adrenal cortex manufactures cortisol, which is essential for regulating stress and metabolism, and aldosterone that regulates blood pressure and levels of salt and water in the body. The adrenal medulla manufactures adrenaline and noradrenaline, which are released during emergencies to prepare the body for the “fight-or-flight” response.
The pancreas, found behind the stomach, is a mixed gland – it produces hormones that increase (glucagon) and decrease (insulin) blood sugar levels. The gonads (testes and ovaries) control male and female secondary sex characteristics, reproduction, and sexual behavior. Testosterone is the male sex hormone, while estrogen and progesterone are female sex hormones.