7.7 - Hormones other than Sex Hormones

Hormones play an important role in regulating various body functions. Apart from sex hormones, there are other hormones secreted by different glands in the body that help in maintaining growth, metabolism, and overall health. These hormones are produced by endocrine glands such as the thyroid, pituitary, and adrenal glands. Let’s explore these hormones in detail.

Thyroid Hormones

The thyroid gland, located in the neck, produces two important hormones: thyroxine (T₄) and triiodothyronine (T₃). These hormones regulate the metabolic rate of the body. They control how quickly the body uses energy, makes proteins, and controls how sensitive the body is to other hormones. They are essential for growth and development, and they also help in maintaining a stable body temperature.

The production of these hormones is controlled by the pituitary gland through the release of Thyroid Stimulating Hormone (TSH). An imbalance in the thyroid hormone levels can lead to disorders such as hypothyroidism (low thyroid hormone levels) and hyperthyroidism (high thyroid hormone levels).

Growth Hormone

The pituitary gland, located at the base of the brain, secretes growth hormone (GH), also known as somatotropin. This hormone is essential for the growth and development of bones and muscles. It stimulates the liver to produce another hormone called insulin-like growth factor (IGF-1), which promotes growth. Growth hormone also plays a role in regulating metabolism by influencing the breakdown of fats and the use of glucose in the body.

The secretion of growth hormone is highest during childhood and adolescence, contributing significantly to the physical growth observed during these stages. Abnormalities in growth hormone secretion can lead to conditions such as gigantism (excessive growth) or dwarfism (insufficient growth).

Insulin

Insulin is a hormone produced by the pancreas. It regulates the levels of glucose (sugar) in the blood. After eating, blood sugar levels rise, and insulin helps in transporting glucose into the cells of the body, where it is used for energy or stored as fat. Insulin is critical for maintaining normal blood sugar levels. A lack of insulin or an inability of the body to respond to insulin leads to diabetes mellitus.

Adrenaline and Noradrenaline

The adrenal glands, located on top of the kidneys, secrete adrenaline (also known as epinephrine) and noradrenaline (norepinephrine). These hormones are involved in the body’s “fight or flight” response. They prepare the body to react to stressful situations by increasing the heart rate, expanding air passages in the lungs, and boosting blood flow to muscles. They also help in increasing the release of glucose for energy.

Adrenaline and noradrenaline are crucial for immediate response to stress but are also involved in regulating blood pressure and heart rate under normal conditions.

Melatonin

Melatonin is a hormone secreted by the pineal gland, located in the brain. It helps in regulating the sleep-wake cycle (circadian rhythm). The production of melatonin increases in response to darkness, promoting sleepiness and helping the body fall asleep. Exposure to light inhibits melatonin secretion, making it easier to stay awake during the day. This hormone plays a key role in maintaining regular sleep patterns.

Cortisol

Cortisol is produced by the adrenal glands and is known as the "stress hormone." It is released in response to stress and low blood glucose levels. Cortisol helps regulate metabolism, immune function, and the body’s response to stress. It also plays a role in controlling the sleep-wake cycle, with higher levels in the morning to help wake the body and lower levels at night to prepare for sleep.

Summary of Key Hormones

• Thyroid Hormones (T₃, T₄) – Regulate metabolism and growth.
• Growth Hormone (GH) – Stimulates growth and regulates metabolism.
• Insulin – Controls blood sugar levels.
• Adrenaline and Noradrenaline – Prepare the body for stress responses.
• Melatonin – Regulates sleep-wake cycles.
• Cortisol – Controls metabolism and stress responses.