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Pharmacology for Nurses

26.1 Introduction to the Adrenal Cortex, Pituitary, and Hypothalamus

Pharmacology for Nurses26.1 Introduction to the Adrenal Cortex, Pituitary, and Hypothalamus

Learning Outcomes

By the end of this section, you should be able to:

  • 26.1.1 Describe the function of the hypothalamus, pituitary gland, and adrenal cortex.
  • 26.1.2 Discuss hormones associated with the hypothalamus, pituitary gland, and adrenal cortex.

Introduction to the Hypothalamus

The hypothalamus is critical to coordinating both nervous and endocrine responses to internal and external stimuli, making it a crucial component of the neuroendocrine system, which is central to regulatory function, as can be seen in Figure 26.2. This section will delve into the intricacies of the hypothalamus by exploring its functions and the hormones it produces.

A flow chart shows that the hypothalamus releases hormones that regulate the function of the anterior pituitary, which regulates metabolism, stress, growth, and reproduction. The hypothalamus also releases hormones that regulate the function of the posterior pituitary, which regulates water balance, blood volume, and sexual functioning.
Figure 26.2 The hypothalamus coordinates neuroendocrine responses from different functions throughout the body. (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

Hypothalamus Function

The hypothalamus gland is located at the base of the forebrain—above the pituitary gland—and serves as a critical regulatory center in the body, responsible for coordinating both nervous and endocrine functions. The hypothalamus controls a range of essential physiological processes, including body temperature, hunger and thirst, water and electrolyte balance, blood pressure, heart rate, sleep and wake cycles, and reproductive behaviors. Additionally, the hypothalamus plays a crucial role in regulating the release of hormones from the pituitary gland, which controls many endocrine functions throughout the body.

Hypothalamus Hormones

The hypothalamus produces and releases several hormones, which play important roles in regulating various physiological processes in the body (Shahid et al., 2022). Some of the major hypothalamus hormones are included in Table 26.1. These hormones are released into the bloodstream and travel to their target organs or glands, where they stimulate or inhibit the release of other hormones or regulate various physiological processes.

Releasing Hormone Associated Hormones Effect
Stimulating Hormones
Gonadotropin-releasing hormone (GnRH) Luteinizing hormone (LH)
Follicle-stimulating hormone (FSH)
Stimulates gamete production and androgen production, which regulates reproductive functions
Thyrotropin-releasing hormone (TRH) Thyroid-stimulating hormone (TSH) Stimulates the thyroid gland to produce hormones and helps to regulate metabolism
Corticotropin-releasing hormone (CRH) Adrenocorticotropic hormone (ACTH) Stimulates the adrenal glands to produce cortisol, a stress hormone
Growth hormone–releasing hormone (GHRH) Growth hormone Promotes growth and development
Prolactin-releasing hormone (PRH) Prolactin (PRL) Promotes lactation from the mammary glands
Inhibitory Hormones
Prolactin-inhibiting hormone (PIH) PRL Inhibits the release of PRL from the pituitary gland
Somatostatin Growth hormone
Inhibits the release of growth hormone and TSH from the anterior pituitary gland
Table 26.1 Hypothalamus Hormones: Releasing and Associated Hormones with Their Effects

Introduction to the Pituitary Gland

The pituitary gland (see Figure 26.3), or pituitary, is a small, pea-sized gland that is a vital part of the endocrine system, regulating various physiological functions in the body. The pituitary, also known as the hypophysis, is located at the base of the brain and is often referred to as the “master gland” because it controls the secretion of hormones by many other glands. The pituitary is divided into two parts, the anterior pituitary and the posterior pituitary, each with unique functions and hormone secretions (Alatzoglou et al., 2020).

The hypothalamus-pituitary complex, located at the base of the brain and shown from a lateral view. The hypothalamus lies inferior and anterior to the thalamus, which is sits atop the brainstem. The hypothalamus connects to the pituitary gland by the stalk-like infundibulum. The pituitary gland looks like a sac containing two balls hanging from the infundibulum. The “balls” are the anterior and posterior lobes of the pituitary. Each lobe secretes different hormones in response to signals from the hypothalamus.
Figure 26.3 The pituitary gland sits at the base of the brain and is considered the “master gland” because of its hormone regulatory actions. (credit: modification of work from Anatomy and Physiology 2e. attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

The anterior pituitary, also known as the adenohypophysis, is the front part of the pituitary. The adenohypophysis is composed of different types of cells that secrete various hormones (see the following section). The anterior pituitary hormones play essential roles in regulating growth and development, metabolism, reproduction, and stress response (Alatzoglou et al., 2020).

The posterior pituitary, also known as the neurohypophysis, is the back part of the pituitary. Unlike the anterior pituitary, it does not synthesize its own hormones, but stores and releases two hormones produced by the hypothalamus: oxytocin and antidiuretic hormone (ADH), also known as human vasopressin. Oxytocin is involved in the contraction of the uterus during childbirth and breast milk ejection during breastfeeding. ADH regulates water balance in the body by controlling the amount of water reabsorbed in the kidneys (Alatzoglou et al., 2020).

Pituitary Function

The pituitary’s primary function is to produce and secrete hormones that act on various organs and tissues throughout the body. Overall, the pituitary assists in regulating various bodily processes and maintaining homeostasis in the body.

Pituitary Hormones

Some of the major hormones produced by the pituitary include:

  • Growth hormone (GH): Promotes the growth and development of bones, muscles, and organs
  • Prolactin (PRL): Stimulates breast milk production
  • Thyroid-stimulating hormone (TSH): Regulates the function of the thyroid gland
  • Adrenocorticotropic hormone (ACTH): Stimulates the adrenal cortex to produce cortisol, which helps the body respond to stress
  • Follicle-stimulating hormone (FSH): Stimulates the development of eggs in females and sperm in males
  • Luteinizing hormone (LH): Regulates the production of sex hormones, including estrogen and testosterone

Introduction to the Adrenal Cortex

The adrenal glands, which are located on top of each kidney, consist of two layers: the adrenal medulla and the adrenal cortex. The adrenal medulla is the inner layer of the adrenal glands and is important for producing epinephrine and norepinephrine in response to stress. This chapter, however, will focus on the adrenal cortex as it relates to endocrine function. The adrenal cortex, as is seen in Figure 26.4, is the outer layer of the adrenal glands. The adrenal cortex produces several important hormones that are essential for proper functioning of the body. Each of the three layers of the adrenal cortex produces a different hormones. The outermost layer is called the zona glomerulosa; the middle layer is called the zona fasciculate; and the innermost layer is called the zona reticularis.

The adrenal gland, located atop the kidney, is composed of an outer cortex and an inner medulla all surrounded by a connective tissue capsule. The cortex can be subdivided into additional zones, all of which produce different types of hormones. The outermost layer is the zona glomerulosa, which releases mineralcorticoids, such as aldosterone, that regulate mineral balance. Underneath this layer is the zona fasciculate, which releases glucocorticoids, such as cortisol, corticosterone and cortisone, that regulate glucose metabolism. Underneath this layer is the zona reticularis, which releases androgens, such as dehydroepiandrosterone, that stimulate masculinization. Below this layer is the adrenal medulla, which releases stress hormones, such as epinephrine and norepinephrine, that stimulate the sympathetic ANS.
Figure 26.4 The adrenal glands produce hormones that are important for regulating body function and the stress response. (credit: modification of work from Anatomy and Physiology 2e. attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

Adrenal Cortex Function

The hormones produced by the adrenal cortex regulate various bodily functions. These hormones maintain the body’s internal environment by regulating electrolyte, pH, and water balance; glucose metabolism; and immune function. Additionally, the adrenal cortex is involved in responding to stressors because its hormones help the body adapt to physical and emotional stress (Huecker et al., 2023; National Institutes of Health [NIH], 2017).

The adrenal cortex’s importance cannot be overstated—it is crucial for maintaining overall health and well-being. Without the hormones from the adrenal cortex, the body would struggle to maintain a stable internal environment, making it vulnerable to various health issues. Therefore, it is essential to maintain the adrenal cortex’s health and function to ensure optimal health and wellness (Huecker et al., 2023; NIH, 2017).

Adrenal Cortex Hormones

Some of the hormones produced by the adrenal cortex include:

  • Mineralocorticoids: produced in the zona glomerulosa, these help regulate the balance of electrolytes, particularly sodium and potassium, in the body as well as water balance.
  • Glucocorticoids: produced in the the zona fasciculate, these help regulate metabolism, immune function, and the body’s response to stress.
  • Androgens: produced in the zona reticularis, these contribute to sexual development and fertility in males.

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