Question

The following hormones are released by hypothalamus except (a) GnRH (b) Somatostatin (c) \(\mathrm{TSH}-\mathrm{RH}\) (d) PRL

Short answer

The hormone among the given options which is not released by hypothalamus is PRL (option d).

Step-by-step solution

Eliminate Known Hypothalamic Hormones

GnRH (Gonadotropin-releasing hormone) is responsible for the release of follicle stimulating hormone and luteinizing hormone from the anterior pituitary. Thyrotropin-releasing hormone (TSH-RH) stimulates the release of thyroid stimulating hormone and prolactin also from the anterior pituitary. Somatostatin is also produced by the hypothalamus and it inhibits the release of growth hormone from the anterior pituitary.

Identify Non-Hypothalamic Hormone

PRL stands for prolactin which is not produced by the hypothalamus but rather, it is produced and released by the anterior pituitary gland. This hormone promotes lactation in females after childbirth.

Key concepts

Hypothalamus Hormones

The hypothalamus is a vital component of the brain. It produces several hormones that play crucial roles in maintaining homeostasis. These hormones act as messengers, instructing other glands and organs on the body's actions. Some of the key hormones released by the hypothalamus include:

• GnRH (Gonadotropin-releasing hormone): This hormone prompts the pituitary gland to produce both follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These hormones are essential for reproductive functions.
• Somatostatin: This hormone inhibits the release of growth hormone (GH) from the pituitary gland. By doing so, it helps regulate the growth processes in the body.
• Thyrotropin-releasing hormone (TSH-RH): It stimulates the release of thyroid stimulating hormone (TSH) and prolactin from the pituitary gland, influencing metabolism and lactation.

These hormones are released in response to signals from the nervous system, reflecting the hypothalamus's role in linking neurological and endocrine functions.

Pituitary Gland

The pituitary gland is a small, pea-sized gland located at the base of the brain, often referred to as the "master gland." This is due to its pivotal role in regulating a multitude of bodily functions by releasing various hormones into the bloodstream. Structurally, it's divided into the anterior and posterior lobes, each responsible for producing different hormones. The anterior pituitary synthesizes and releases hormones such as:

• Prolactin: Important for milk production post-pregnancy.
• Growth Hormone (GH): Influences physical growth and development.
• Thyroid Stimulating Hormone (TSH): Stimulates thyroid gland activities.

Meanwhile, the posterior lobe stores and releases hormones produced by the hypothalamus, like vasopressin and oxytocin. The pituitary works in harmony with the hypothalamus, responding to its signals to maintain bodily equilibrium.

Prolactin

Prolactin is a hormone primarily associated with lactation. After childbirth, prolactin levels rise, signaling the mammary glands to produce milk for breastfeeding. While the anterior pituitary gland produces prolactin, its regulation is primarily managed by the hypothalamus. Notably, prolactin's functions are not confined to lactation. It plays a role in over 300 different biological processes. Some of these include:

• Regulating the immune system.
• Contributing to reproductive functions in both men and women.
• Helping manage metabolism and behaviors like bonding and stress response.

Understanding prolactin's multifaceted roles underscores its importance beyond simply being a component of the lactation process.

Hormone Regulation

Hormone regulation is a complex and dynamic process, crucial for maintaining bodily balance. The hypothalamus and pituitary gland team up effectively to control hormone levels and ensure that each hormone is released when needed. Hormone regulation involves:

• Feedback mechanisms: These are systems within the body that monitor hormone levels. For instance, when a hormone's level becomes high, a feedback mechanism signals to decrease the production of that hormone, preventing imbalances.
• Hypothalamic control: The hypothalamus receives signals from the body, sending instructions through releasing or inhibiting hormones to the pituitary gland.
• Pituitary response: The pituitary gland reacts to signals from the hypothalamus by adjusting its secretion of hormones, coordinating the body's reactions to various stimuli.

This regulation is vital for processes such as growth, metabolism, and reproduction, ultimately affecting growth rates, energy production, and reproductive health.