Discovery Science: Human – Metabolism and Hormones – Hormones

Earth Science: Human – Metabolism and Hormones – Hormones

Hormones are information carriers in the human body. Instead of the electrical impulses used by the nervous system, the hormone system uses chemical messenger substances and is, therefore, much slower.

Hormones are signaling molecules, responsible for regulating bodily functions, sending messages, and acting on organs and tissues. Moreover, hormones regulate functions as disparate as mood, growth, reproduction, and metabolism. The majority of hormones are generated in the endocrine glands, such as the thyroid gland, hypophysis (pituitary gland), or the pancreas.

In addition, some tissue cells can also produce hormones, such as the cells of the stomach lining. The glands usually release hormones into the bloodstream, where they travel through the body to act as required. The hypophysis is of special importance, as the hormones of the hypophysis regulate the activities of other endocrine glands.

Hormones may be a range of molecular types, including peptide hormones such as insulin, steroid hormones such as estrogen, and hormones composed of amino acids such as adrenaline.

Interaction of the hormones and nervous system

The hormone system and the nervous system are responsible for relaying information within the body and triggering reactions. The nervous system is mainly responsible for quick reactions, with transfer speeds of up to 268 miles per hour (120 m/s).

The hormone system is designed for more long-term effects, with transfer speeds of about 0.2 inch per second (five mm/s). Some nerve cells can produce hormones.

Humans have such neurosecretory cells in the hypothalamus, where hormonal and neural mechanisms are regulated and coordinated.

How hormones work

The way hormones work is best explained by an example: regulation of the blood sugar level. After eating a meal rich in carbohydrates, insulin is released by the pancreas in response to high blood sugar levels. Insulin causes the liver and muscles to take in glucose and store it as glycogen, which then lowers the blood sugar level.

Glucagon, another hormone released by the pancreas, has the opposite effect. Released in response to low blood sugar levels, it increases the blood sugar level by accelerating breakdown of the sugar glycogen to glucose in the liver and muscles, as occurs during heavy exercise.


When using hormonal birth control pills, the hypophysis is tricked into thinking that the woman taking the pills is pregnant. This is achieved through a combination of various hormones, primarily estrogen and progesterone.

The hypophysis will then reduce production of the luteinizing hormone (LH), which usually triggers ovulation during the normal female cycle. If ovulation does not occur, pregnancy is impossible.


HUMAN GROWTH HORMONES are sometimes used for doping to increase an athlete’s performance.

This practice is dangerous as well as unethical: it may result in death due to an increased risk of heart attacks, diabetes, and perhaps also cancer.