Endocrine glands

Answer 1

Definition

Endocrine glands release hormones into the bloodstream.

Endocrine glands include the:

• Adrenal
• Hypothalamus
• Islets of Langerhans in the pancreas
• Ovaries
• Parathyroid
• Pineal
• Pituitary
• Testes
• Thyroid

Information

When a gland releases a substance, it is called secretion. Hypersecretion is when too many hormones are released. Hyposecretion is when too few hormones are released.

Many different disorders can result when too few hormones or too many hormones are released.

Here is a partial list of disorders that may result when a particular gland does not produce the right amount of hormones.

Adrenal:

• Addison's disease
• Adrenogenital syndrome
• Cushing syndrome
• Pheochromocytoma

Pancreas:

• Diabetes
• Hypoglycemia

Parathyroid:

• Tetany
• Renal calculi
• Excessive loss of minerals from bone

Pituitary:

• Growth hormone deficiency
• Acromegaly
• Diabetes
• Gigantism
• Diabetes insipidus

Testes and ovaries:

• Lack of sex development (unclear genitalia)

Thyroid:

• Congenital hypothyroidism
• Myxedema
• Goiter
• Thyrotoxicosis

References

Gill GN, Clemmons DR. Principles of endocrinology. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 240.

Answer 2

The endocrine system is primarily composed of glands that produce chemical messengers called hormones. Glands of the endocrine system include the pituitary gland, the thyroid gland, the parathyroid glands, the thymus, and the adrenal glands.

Other glands are also included within the endocrine system since they contain endocrine tissue that secretes hormones. These include the pancreas, ovaries and testes.

The endocrine and nervous systems work very closely together. The brain continuously sends instructions to the endocrine system, and in return receives feedback from the endocrine glands. Because of this intimate relationship, the nervous and endocrine systems are referred to as the neuroendocrine system.

The hypothalamus is known as the master switchboard because it's the part of the brain that controls the endocrine system. The pituitary gland, which hangs by a thin stalk from the hypothalamus, is called the master gland of the body because it regulates the activity of the endocrine glands.

The hypothalamus detects the rising level of the target organ's hormones then sends either hormonal or electrical messages to the pituitary gland. In response, the pituitary gland releases hormones, which travel through the bloodstream to a target endocrine gland, instructing it to stop producing its hormones.

Here's how the endocrine system keeps itself in check: eventually, the hypothalamus detects the rising level of the target organ's hormones, and sends a message to the pituitary gland. The pituitary gland then stops releasing certain hormones, causing the target organ to stop producing its hormones.

The endocrine system constantly adjusts hormone levels so that the body can function normally. This process is called homeostasis.

Reviewed By

Review Date: 05/01/2011

Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

Answer 3

Definition

Endocrine glands release hormones into the bloodstream.

Endocrine glands include the:

• Adrenal
• Hypothalamus
• Islets of Langerhans in the pancreas
• Ovaries
• Parathyroid
• Pineal
• Pituitary
• Testes
• Thyroid

Information

When a gland releases a substance, it is called secretion. Hypersecretion is when too many hormones are released. Hyposecretion is when too few hormones are released.

Many different disorders can result when too few hormones or too many hormones are released.

Here is a partial list of disorders that may result when a particular gland does not produce the right amount of hormones.

Adrenal:

• Addison's disease
• Adrenogenital syndrome
• Cushing syndrome
• Pheochromocytoma

Pancreas:

• Diabetes
• Hypoglycemia

Parathyroid:

• Tetany
• Renal calculi
• Excessive loss of minerals from bone

Pituitary:

• Growth hormone deficiency
• Acromegaly
• Diabetes
• Gigantism
• Diabetes insipidus

Testes and ovaries:

• Lack of sex development (unclear genitalia)

Thyroid:

• Congenital hypothyroidism
• Myxedema
• Goiter
• Thyrotoxicosis

References

Kronenberg HM, Melmed S, Larsen PR, Polonsky KS. Principles of endocrinology. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. Philadelphia, Pa: Saunders Elsevier; 2008:chap 1.

Reviewed By

Review Date: 05/01/2011

Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.