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Course: Fundamentals of Nursing�Topic: Endocrine System

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Module Goals

Learners will be able to:

Identify the organs that comprise the endocrine system.
Describe the functions of the endocrine system related to the support of physiological functioning (Basic Human Needs).
Describe normal endocrine changes across the lifespan.
Interpret laboratory values used to assess endocrine function.

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Endocrine System

National Cancer Institute, n.d

There are eight major endocrine glands scattered throughout the body, they are still considered to be one system.

Endocrine system is made up of endocrine glands and secret hormone.

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Endocrine System

The endocrine glands:

Pituitary gland
Thyroid gland
Parathyroid glands
Adrenal glands
Pineal glands
Thymus gland
Ovaries
Testes

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Functions of Endocrine Glands

Secrete hormones directly into the surrounding fluid that play role in homeostasis.
Functions of Hormones include:

Coordinate and control growth
Metabolism
Temperature regulation
The stress response
Reproduction, and many other functions

Some have both endocrine and non-endocrine functions:

Example, the pancreas helps in digestion as well as secrete the hormones insulin and glucagon, which regulate blood glucose levels.

Gordon Betts et al., 2013

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Pituitary and Pineal Glands

Gordon Betts et al., 2013

There are two distinct regions in the pituitary gland:

the Anterior lobe (adenohypophysis)
the Posterior lobe (neurohypophysis)

The activity of the adenohypophysis is controlled by releasing hormones from the hypothalamus.
The neurohypophysis is controlled by nerve stimulation.

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Hormones of the Anterior Lobe

Growth hormone (GH): Promotes growth of body tissues.
Thyroid-stimulating hormone (TSH): Stimulates thyroid hormone release from thyroid.
Adrenocorticotropic hormone (ACTH): Stimulates hormone release by adrenal cortex.
Prolactin (PRL): Promotes milk production from mammary glands.
Follicle-stimulating hormone (FSH): Stimulates gamete production in gonads.
Luteinizing hormone (LH): Stimulates androgen production by gonads.

Gordon Betts et al., 2013

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Critical Thinking Question

The secretion of thyroid hormones is controlled by ________.

TSH from the hypothalamus
TSH from the anterior pituitary
thyroxine from the anterior pituitary
thyroglobulin from the thyroid’s parafollicular cells

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Hormones of the Pituitary Lobe

Gordon Betts et al., 2013

Antidiuretic hormone (ADH): Stimulates water reabsorption by kidneys.
Oxytocin: Stimulates uterine contractions during childbirth.

Intermediate Zone:
Melanocyte-stimulating hormone: Stimulates melanin formation in melanocytes.

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Thyroid Gland

Gordon Betts et al., 2013

Thyroxine (T4), triiodothyronine (T3): Stimulate basal metabolic rate.

Calcitonin that is produced by the parafollicular cells (also called C cells):

released in response to a rise in blood calcium levels.
Reduces blood Ca2+ levels.

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Thyroid Gland

Gordon Betts et al., 2013

Dietary iodine deficiency can result in the impaired ability to synthesize T3 and T4, When T3 and T4 cannot be produced, TSH is secreted in increasing amounts.

This results increases the overall size of the thyroid gland, a condition called a goiter.

Other iodine deficiency disorders are impaired growth and development, decreased fertility, and prenatal and infant death.

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Critical Thinking Question

Which of the following is an anterior pituitary hormone?

ADH
oxytocin
TSH
cortisol

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Parathyroid Gland

The tiny, round structures usually found embedded in the posterior surface of the thyroid gland.
Produce and secrete the parathyroid hormone (PTH).
Parathyroid hormone increases blood calcium levels when they drop too low.

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Adrenal Gland

Gordon Betts et al., 2013

Both are located at the top the kidneys
Composed of an outer cortex and an inner medulla.
The adrenal cortex: ACTH stimulate cortex to produce the hormone cortisol

Regulation of the long-term stress response, blood pressure and blood volume, nutrient uptake and storage, fluid and electrolyte balance, and inflammation.

The adrenal medulla:

Secrets epinephrine and norepinephrine.

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Hormones of Adrenal Gland

The Cortex:

Aldosterone (the major mineralocorticoid).
Are essential for fluid and electrolyte balance.
A key component of the renin-angiotensin-aldosterone system (RAAS) for regulating blood pressure.

Epinephrine and norepinephrine:

Signal the liver and skeletal muscle cells to convert glycogen into glucose, resulting in increased blood glucose levels.
Increase the heart rate, pulse, and blood pressure to prepare the body to fight the perceived threat or flee from it.

Gordon Betts et al., 2013

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Disorder of Adrenal Gland

Hyperglycemia:

Risk of developing type 2 diabetes
In addition chronically elevated glucocorticoids:

Compromise immunity,
Resistance to infection
can result in rapid weight gain and hair loss

Cushing’s Syndrome: Caused by hypersecretion of cortisol and Characterized by:

High blood glucose
A moon-shaped face,
A buffalo hump on the back of the neck,
Rapid weight gain, and hair loss

Gordon Betts et al., 2013

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Critical Thinking Question

The adrenal glands are attached superiorly to which organ?

thyroid
liver
kidneys
hypothalamus

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Disorder of Adrenal Gland

Addison’s Disease: (the hyposecretion of corticosteroids)

A rare disorder that causes low blood glucose levels and low blood sodium levels
Signs and symptoms:

General weakness,
Abdominal pain,
Weight loss,
Nausea/vomiting
Sweating
Cravings for salty food

Gordon Betts et al., 2013

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Pineal Gland

Gordon Betts et al., 2013

Is located inferior and posterior to the thalamus.
The pinealocyte cells that make up the pineal gland are known to produce and secrete melatonin in response to low light levels.
Melatonin may influence

the body’s circadian rhythms.
the dark-light fluctuations that affect not only sleepiness and wakefulness, but also appetite and body temperature.

High blood levels of melatonin induce drowsiness.

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Gonadal Hormone

Gordon Betts et al., 2013

Testes:

Testosterone is the primary hormone.
Roles of testosterone include:

Development of the male reproductive system,
The maturation of sperm cells
The development of male secondary sex characteristics such as a deepened voice, body hair, and increased muscle mass

Interestingly, testosterone is also produced in the female ovaries, but at a much reduced level.

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Gonadal Placental Hormone

Gordon Betts et al., 2013

Ovaries:The primary hormone is estrogen.

Estrogen: plays an important role in:

The development of the female reproductive system,
Regulation of the menstrual cycle,
The development of female secondary sex characteristics:
increased adipose tissue and the development of breast tissue, and
the maintenance of pregnancy

Progesterone: Regulation of the menstrual cycle, preparing the body for pregnancy as well as maintaining pregnancy.

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Placental Hormone

Produces human chorionic gonadotropin (hCG).
The hCG hormone promotes progesterone synthesis and reduces the mother’s immune function to protect the fetus from immune rejection.
It also secretes human placental lactogen (hPL), which plays a role in:

Preparing the breasts for lactation, and
Relaxin, which is thought to help soften and widen the pubic symphysis in preparation for childbirth.

Gordon Betts et al., 2013

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Pancreatic Hormone

Primarily an exocrine gland, secreting a variety of digestive enzymes.
The pancreatic islets—the islets of Langerhans—secrete the hormones glucagon, insulin, somatostatin, and pancreatic polypeptide (PP).

Insulin (beta cells): Reduces blood glucose levels.
Glucagon (alpha cells): Increases blood glucose levels.
Somatostatin (delta cells): Inhibits insulin and glucagon release.
Pancreatic polypeptide (PP cells): Role in appetite.

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Gordon Betts et al., 2013

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Pancreatic Endocrine Disorders

Diabetes Mellitus:

Dysfunction of the production of insulin characterized by high blood glucose levels.
There are two main forms of diabetes mellitus.

Type 1 diabetes:

An autoimmune disease affecting the beta cells of the pancreas.
The beta cells do not produce insulin; thus, synthetic insulin must be administered by injection or infusion.

Type 2 diabetes:

Acquired, and lifestyle factors such as poor diet, inactivity, and the presence of pre-diabetes greatly increase a risk.

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Lab Tests for Endocrine System

Blood Tests:

Blood Sugar Test: test to detect diabetes and prediabetes.
Glycosylated hemoglobin test (A1c)

Thyroid Stimulating Hormone (TSH):

Changes in TSH can serve as an “early warning system” – often occurring before the actual level of thyroid hormones in the body becomes too high or too low.
A high TSH level indicates: Hypothyroidism.
TSH level is low, usually indicates that the thyroid is producing too much thyroid hormone (hyperthyroidism).

American Thyroid Association, 2021

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Critical Thinking Question

Cushing’s disease is a disorder caused by ________.

abnormally low levels of cortisol
abnormally high levels of cortisol
abnormally low levels of aldosterone
abnormally high levels of aldosterone

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Lab Tests for Endocrine System

Tests for luteinizing hormone (LH) and follicle stimulating hormone (FSH) can help to detect female hormonal issues.
Other blood tests detect levels of hormones:

Cortisol, 17 hydroxyprogesterone, DHEA-sulfate, ACTH, aldosterone, vitamin D, PTH, prolactin and various forms of estrogen, that affect different systems.

Tests for thyroglobulin (Tg) levels can monitor thyroid cancer.

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Endocrine System Tests

Fine Needle Aspiration (FNA): A thin needle is inserted into the area a thyroid nodule. It is often performed under ultrasound guidance.
Sestamibi scan

A nuclear medicine scan that detects abnormally enlarged parathyroid glands after radioactive dye is injected into the bloodstream.
This test can locate parathyroid adenoma (benign tumors).

University of Iowa Health Care, 2021

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Endocrine System Tests

Ultrasound

To detect masses or fluid in soft tissues.
Useful in evaluating thyroid nodules, lymph nodes in the neck, and can identify enlarged parathyroid glands.

Endoscopic Ultrasound

Useful to localize small pancreatic neuroendocrine tumors, especially insulinomas (a rare, insulin producing tumor of the pancreas).

Radioactive Iodine Scan (RAI)

Sensitive test for the detection of normal and most cancerous thyroid cells both in the neck and throughout the rest of the body.

University of Iowa Health Care, 2021

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References:

American Thyroid Association, 2021. Thyroid Function Tests. https://www.thyroid.org/thyroid-function-tests /

Gordon Betts et al., (2013). Anatomy and Physiology. OSCRiceUniversity is licensed under a Creative Commons Attribution 4.0.

SEER Training Modules, Cancer Registration and Surveillance Module, Anatomy and Physiology. Endocrine system: Endocrine glands and Their Hormones . U. S. National Institutes of Health, National Cancer Institute. (27 July 2021) <https://training.seer.cancer.gov/>

University of Iowa Health Care, 2021.Endocrine system diagnostic tests. https://uihc.org/health-topics/endocrine-system-diagnostic-tests

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