Hormones

Hormones are chemical messengers produced by specialized cells, organs or tissues in the body, usually in glands of the endocrine system. They regulate a variety of biological processes by sending messages to target cells or organs that perform specific functions.

Function of hormones

Hormones act as regulators and influence many vital processes such as:

• Growth and development
• Metabolism and energy balance
• Reproduction and sexual function
• Mood and emotions
• Homeostasis (maintenance of internal balance)

How do hormones work?

Hormones are released into the blood or lymphatic fluid and reach their target cells via the bloodstream. There they dock onto specific receptors that function like locks. The interaction between hormone and receptor triggers a specific reaction in the target cell.

Types of hormones

Hormones can be categorized according to their chemical structure or function:

According to chemical structure

• Peptide hormones: Consist of amino acids. Examples: Insulin, glucagon.
• Steroid hormones: Derived from cholesterol. Examples: Testosterone, oestrogen.
• Amino acid derivatives: Formed from a single amino acid. Examples: Adrenaline, thyroxine.
• Fatty acid derivatives: examples: Prostaglandins.

By function

• Growth hormones: Promote growth and cell division (e.g. somatotropin).
• Sex hormones: regulate reproduction and sexual development (e.g. oestrogen, progesterone, testosterone).
• Stress hormones: help the body to react to stress (e.g. adrenaline, cortisol).
• Metabolic hormones: Control energy production and consumption (e.g. insulin, glucagon, thyroid hormones).

Important endocrine glands in the body

Hormones are produced by specialized glands of the endocrine system. The most important of these include

Hypothalamus

• Produces hormones that control the pituitary gland (e.g. gonadotropin-releasing hormone).
• Controls many vital functions, such as appetite, sleep and body temperature.

Pituitary gland (hypophysis)

• Produces hormones such as somatotropin (growth hormone) and prolactin.
• Often referred to as the “master gland” because it regulates many other glands.

Thyroid gland

• Produces thyroxine (T4) and triiodothyronine (T3), which influence the metabolism.
• Hormone production is controlled by the thyroid-stimulating hormone (TSH) of the pituitary gland.

Parathyroid glands

• Produce parathyroid hormone, which regulates calcium and phosphate metabolism.

Adrenal gland

• Consists of two parts
  • Adrenal cortex: Produces cortisol and aldosterone.
  • Adrenal medulla: Produces adrenaline and

Pancreas (pancreas)

• Produces insulin and glucagon, which regulate blood sugar levels.

Gonads (gonads)

• Ovaries: Produce oestrogen and progesterone.
• Testicles: Produce testosterone.

Pineal gland (pineal gland)

• Produces melatonin, which controls the sleep-wake rhythm.

Hormones do not have a uniform “appearance” as they consist of different chemical structures. Their form and composition depend on their type and function. Nevertheless, some basic properties and examples of chemical structures can be described:

Visualization of hormones

Scientists use chemical models to visualize hormones. These models show the atoms (such as carbon, hydrogen, oxygen and nitrogen) as spheres or circles connected by lines (bonds). Examples of such models are

• Ball-and-stick models: atoms as balls, bonds as sticks.
• Molecule models with surfaces: Show the three-dimensional shape and charge distribution.

Size of hormones

Hormones are tiny compared to cells:

• Peptide hormones: Are somewhat larger, as they consist of many atoms.
• Steroid hormones and amino acid derivatives: Very small, consist of only a few dozen atoms.

So if hormones were visible, they could be described as molecular tools with different shapes: from long chains (as in peptide hormones) to compact rings (in steroid hormones) to small, compact molecules (in amino acid derivatives).

Regulation of hormones

Hormone production and release are controlled by feedback mechanisms:

• Negative feedback: An increased concentration of a hormone signals the gland to reduce production (e.g. insulin in the case of high blood sugar).
• Positive feedback: Increases hormone production until a goal is reached (e.g. oxytocin at birth).

Hormonal disorders

An imbalance in hormone production can cause significant health problems:

Overproduction of hormones

• Hyperthyroidism: hyperthyroidism leads to weight loss and nervousness.
• Cushing’s syndrome: overproduction of cortisol causes weight gain and high blood pressure.

Underproduction of hormones

• Hypothyroidism: hypothyroidism leads to tiredness and weight gain.
• Type 1 diabetes: Insulin deficiency leads to increased blood sugar.

Hormone resistance

• Target cells do not react to hormones even though they are present (e.g. insulin resistance in type 2 diabetes).

Hormonal influences on behavior

Hormones not only influence physical processes, but also emotions, behavior and social interactions:

• Oxytocin: Promotes bonding and trust.
• Adrenaline: Strengthens the fight-or-flight response.
• Serotonin: Boosts mood and well-being.

More facts about hormones

• Hormones often work in very low concentrations, but with great effectiveness.
• Hormones often interact with each other – they can reinforce or inhibit each other.
• The hormone balance changes in the course of life, e.g. during puberty, pregnancy and in old age.

The future of hormone research

Modern approaches such as personalized medicine and biotechnological developments make this possible:

• Targeted hormone therapies: For the treatment of conditions such as diabetes, hormonally induced infertility or thyroid problems.
• Real-time hormone monitoring: wearables could soon measure hormone levels and provide early warning of imbalances.
• New synthetic hormones: Could replace natural hormones or control their effect more precisely.

Conclusion

Hormones are necessary for the functioning of the body and influence almost every aspect of our lives. Understanding how they work and how they are regulated is crucial to recognizing and treating hormonal disorders.