Difference Between Adrenal Gland and Pituitary Gland

Main Difference – Adrenal gland vs Pituitary Gland

Adrenal gland and pituitary gland are two types of endocrine glands in animals. Endocrine glands produce hormones and secrete them directly to the blood in order to be transported to the target organ. They are ductless glands. Endocrine glands are categorized into primary and secondary endocrine glands. Primary endocrine glands secrete hormones to regulate the production and release of hormones of the secondary endocrine glands. The main difference between adrenal gland and pituitary gland is that adrenal gland is a secondary endocrine gland whereas pituitary gland is a primary endocrine gland. The production and release of hormones in the adrenaline gland are regulated by the pituitary gland and the sympathetic nervous system. The hypothalamus controls the release of hormones from the pituitary gland.

Key Areas Covered

1.What is Adrenal Gland
      – Definition, Anatomy, Function
2.What is Pituitary Gland
      – Definition, Anatomy, Function
3.What are the Similarities Between Adrenal Gland and Pituitary Gland
      – Outline of Common Features
4.What is the Difference Between Adrenal Gland and Pituitary Gland
      – Comparison of Key Differences

Key Terms: Adrenal Cortex, Adrenal Gland, Adrenal Medulla, Aldosterone, Anterior Pituitary Gland, Cortisol, Hypophysis, Master Gland, Pituitary Gland, Posterior Pituitary Gland

What is Adrenal Gland

Adrenal gland is a small gland located on top of the kidney. There is a pair of adrenal glands in the human body. The adrenal gland is a triangular-shaped organ with 1.5 inches in height and 3 inches in length. Two distinct cell layers can be identified inside the Adrenal Gland: adrenal cortex and adrenal medulla. The adrenal cortex is the firm, outer part of the adrenal gland. It mainly secretes two groups of enzymes: glucocorticoids and mineralocorticoids. The two types of glucocorticoids secreted by the adrenal cortex are cortisol and corticosterone. These two enzymes regulate the metabolism of proteins and fats under stressful conditions. The production and secretion of glucocorticoids are regulated by the hypothalamus and pituitary gland. The aldosterone is the mineralocorticoid secreted by the adrenal cortex, regulating the water and salt balance of the blood. The production and secretion of mineralocorticoids are regulated by the sympathetic nervous system. The structure and the hormones secreted by the adrenal gland are shown in figure 1.

Figure 1: Structure of Adrenal Gland and Hormones Secreted by it

The adrenal medulla is the soft, inner part of the adrenal gland. The two hormones secreted by the adrenal medulla are adrenaline and noradrenaline. These hormones are secreted to mediate the fight-or-flight mechanisms in acute stress conditions. Adrenaline is also called epinephrine. It increases the glucose levels in the blood. Adrenaline also increases the blood pressure and the heart rate and supplies more glucose and oxygen to the brain and muscles. Noradrenaline mediates the vasoconstriction to increase blood pressure.

What is Pituitary Gland

The pituitary gland is the major endocrine gland of the body. Hormones secreted by the pituitary gland regulate the production and secretion of hormones of the rest of the endocrine glands in the body. The pituitary gland is a pea-sized gland found at the base of the brain, inferior to the hypothalamus and posterior to the bridge of the nose. The pituitary gland is also called the hypophysis. The pituitary gland is connected to the hypothalamus by a tiny isthmus of nerve tissue called infundibulum. The two functional components of the pituitary gland are anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis). The anterior pituitary gland produces and secretes hormones. But, the posterior pituitary gland stores and secretes hormones produced by the hypothalamus.

The structure of the pituitary gland is shown in figure 2.

Figure 2: Pituitary Gland

The anterior pituitary gland secretes seven important hormones, inducing the secondary endocrine glands to produce and secrete hormones. Therefore, the pituitary gland is called the master gland. The hormones secreted by the anterior pituitary gland and their target organs are described in table 1.

Anterior Pituitary Hormones and their Target Organs

The hormones released by the hypothalamus regulate the release of hormones of the pituitary gland. They are thyrotrophin-releasing hormone (TRH), gonadotropin-releasing hormone (GnRH), and growth hormone-inhibiting hormone (GHIH).

Similarities Between Adrenal Gland and Pituitary Gland

• Both adrenal gland and pituitary gland are two types of endocrine glands.
• Both adrenal gland and pituitary gland produce and secrete hormones to the blood.

Difference Between Adrenal Gland and Pituitary Gland

Definition

Adrenal Gland: Adrenal gland is a small gland located on top of the kidney, producing hormones to regulate heart rate, blood pressure, and metabolism of the body under stressful conditions.

Pituitary Gland: Pituitary gland is the major endocrine gland of the body, which is attached to the base of the brain and controls the growth, development, and functions of the rest of the endocrine glands in the body.

Location

Adrenal Gland: Adrenal gland is situated on top of the kidney.

Pituitary Gland: Pituitary gland is situated at the base of the brain.

Number of Glands per Body

Adrenal Gland: There are two adrenal glands in the body.

Pituitary Gland: There is only one pituitary gland in the body.

Primary/Secondary Gland

Adrenal Gland: Adrenal gland is a secondary endocrine gland.

Pituitary Gland: Pituitary gland is the major primary endocrine gland in the body.

Components

Adrenal Gland: Adrenal gland is composed of adrenal cortex and adrenal medulla.

Pituitary Gland: Pituitary gland is composed of the anterior pituitary gland and posterior pituitary gland.

Regulation

Adrenal Gland: The release of hormones from the adrenal gland is regulated by the pituitary gland, hypothalamus, and the sympathetic nervous system.

Pituitary Gland: The release of hormones from the adrenal gland is regulated by the hypothalamus.

Conclusion

Adrenal gland and pituitary gland are two types of endocrine glands, which secrete hormones to regulate the functions of the body. The pituitary gland regulates the production and release of hormones of most of the endocrine glands in the body. Therefore, it is a primary endocrine gland. The hormones of the endocrine gland do not regulate the functions of the other endocrine glands. Therefore, it is a secondary endocrine gland. This is the main difference between adrenal gland and pituitary gland.

Reference:

1. “An Overview of the Adrenal Glands.” EndocrineWeb, Available here. Accessed 13 Sept. 2017.
2. “Pituitary Gland.” InnerBody, Available here. Accessed 13 Sept. 2017.
3. “Overview of the Pituitary Gland – Hormonal and Metabolic Disorders.” Merck Manuals Consumer Version, Available here. Accessed 13 Sept. 2017.

Image Courtesy:

1. “1818 The Adrenal Glands” By OpenStax College – Anatomy & Physiology, Connexions Web site. Available here, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia
2. “1806 The Hypothalamus-Pituitary Complex” By OpenStax College – Anatomy & Physiology, Connexions Web site. Available here, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia