Endocrine System Vocabulary

Endocrine System

Introduction

• The nervous and endocrine systems are closely related and share similar objectives.
• The endocrine system focuses on anatomical and disease terms.

Learning Objectives

• Refer to the book chapter for a list of learning objectives.

What is the Endocrine System?

• Endo means "within."
• Crin/crine means "to secrete."
• The endocrine system secretes products within the body, specifically into the blood.
• This is in contrast to exocrine glands, which secrete products onto the body's outer surfaces (e.g., mammary glands, oil glands, sweat glands).
• Endocrine glands produce hormones that are secreted into the bloodstream.

Neuroendocrine System

• The endocrine and nervous systems work together to control bodily processes.

• Combined, they are referred to as the neuroendocrine system.

• Their function is to maintain homeostasis, achieving balance in bodily processes.

  • Examples: regulating blood sugar, blood pressure, and blood calcium levels.

Comparison of Nervous and Endocrine Systems

• Both systems aim to maintain homeostasis but differ in tissue composition and speed.
• The nervous system comprises the brain, spinal cord, nerves, ganglia, and receptors.
• The endocrine system consists of various glands throughout the body.
• The nervous system is fast-acting, using electrical signals and neurotransmitters to control functions rapidly (sometimes in fractions of a second).
• The endocrine system is slower, using hormones secreted into the blood to reach target tissues.

Endocrine Glands

• Endocrine glands are ductless, secreting hormones directly into the bloodstream.

• Examples of glands and organs include:

  • Pineal gland
  • Pituitary gland
  • Thyroid
  • Parathyroid glands
  • Thymus
  • Adrenal glands
  • Pancreas
  • Testes/Ovaries

Location of Endocrine Organs

Brain

• Pineal gland: Located posterior to the thalamus in the diencephalon; produces melatonin, which regulates the sleep-wake cycle.
• Pituitary gland: A small gland (pea-sized) dangling off the hypothalamus, considered a master gland, though controlled by the hypothalamus.

Neck and Chest

• Thyroid: The largest endocrine gland, located in the cervical region, hugging the trachea under the larynx. On the backside of the thyroid are the parathyroid glands.
• Parathyroid glands: Usually four glands attached to the back of the thyroid, regulating blood calcium levels.
• Thymus: Located on top of the heart; produces thymosins and has immune system functions; shrinks with age.

Abdominal Area

• Adrenal glands: Also called suprarenal glands because they sit on top of the kidneys; aid in combating stress.
• Pancreas: Contains small patches of endocrine tissue called pancreatic islets (islets of Langerhans), which produce insulin and glucagon to regulate blood glucose levels; most of the pancreas has digestive functionality.

Reproductive Organs

• Testes: Produce androgens, primarily testosterone.
• Ovaries: Produce estrogens, the female sex hormones.

Endocrine Organs and Their Functions

• The pituitary gland is small but critical, secreting many hormones.
• The islets of Langerhans are also called pancreatic islets.

Thyroid and Parathyroid Glands

• The thyroid is bilobed, with a lobe on each side connected by the isthmus.
• It is positioned under the larynx, where the thyroid cartilage is located.
• You should not normally be able to see the thyroid poking through someone's skin unless it's enlarged, which could mean that you have a disorder
• Parathyroid glands are attached to the back of the thyroid.
• The function and existence of parathyroid glands have not been known about for very long because people did not know they existed until thyroidectomies started leading to physiological problems that were unrelated to thyroid function.

Pancreas

• The pancreas has a head, neck, body, and tail.
• Alpha cells in the pancreatic islets produce glucagon, which raises blood glucose levels.
• Beta cells produce insulin, which lowers blood glucose levels.
• Insulin and glucagon are antagonistic hormones that regulate blood glucose levels.

Pituitary Gland

• The pituitary gland is a small but important organ connected to the hypothalamus by a stalk.

• It has two parts:

  • Anterior pituitary (adenohypophysis): The glandular section.
  • Posterior pituitary (neurohypophysis): Made of nervous tissue.

• The hypothalamus controls the pituitary gland.

• The posterior pituitary only stores hormones (ADH and oxytocin) that are actually made by the hypothalamus.

• The relationship between the hypothalamus and pituitary is called the hypothalamic-pituitary axis.

Anterior Pituitary Hormones

• Thyroid-stimulating hormone (TSH): Targets the thyroid.
• Adrenocorticotropic hormone (ACTH): Targets the adrenal cortex.
• Follicle-stimulating hormone (FSH) and luteinizing hormone (LH): Target reproductive organs.
• Growth hormone (GH): Targets bones, muscles, and other tissues to promote growth.
• Prolactin (PRL): Stimulates milk production in mammary glands.

Posterior Pituitary Hormones

• Oxytocin: Aids in labor and delivery by contracting the uterus and helps release milk (let-down reflex); also involved in bonding.
• ADH (antidiuretic hormone) / Vasopressin: Targets the kidney to retain water; also constricts arterioles to increase blood pressure.

Pineal Gland

• Located in the diencephalon.
• Produces melatonin to regulate sleep.

Thyroid Gland

• Located in the neck.
• Produces T3 (triiodothyronine) and T4 (thyroxine) to regulate basal metabolic rate (BMR).
• Common thyroid problems include hyperthyroidism (overproduction of thyroid hormones) and hypothyroidism (underproduction of thyroid hormones).

Parathyroid Glands

• Located on the backside of the thyroid.
• Produce parathyroid hormone (PTH) to regulate blood calcium levels.

Islets of Langerhans (Pancreas)

• Glucagon: Increases blood glucose levels.
• Insulin: Decreases blood glucose levels.

Thymus Gland

• Produces thymosins, which play a role in immune system responses.

Adrenal Gland

• Also called the suprarenal gland.

• Located on top of the kidneys.

• Has two parts:

  • Adrenal cortex (outer): Produces cortisol to reduce inflammation and increase blood glucose levels and aldosterone to regulate mineral and electrolyte balance and blood pressure.
  • Adrenal medulla (inner): Produces epinephrine (adrenaline) and norepinephrine (noradrenaline), which elicit the fight-or-flight response.

Ovaries and Testes

• Ovaries: Produce estrogen.
• Testes: Produce testosterone.
• These hormones have various effects, which will be covered in later chapters.

Combining Forms

• acro-: tip, extremity
• adeno-: gland
• adreno- / adrenalo-: adrenal glands
• calci-: calcium
• cortico-: cortex
• crino- / crino-: to secrete
• dipso-: thirst
• endocrino-: endocrine
• gluco- / glucoso- / glyco- / glycoso-: sugar, glucose
• hormono-: hormone
• kali-: potassium
• natri-: sodium
• pancreato-: pancreas
• parathyroido-: parathyroid glands
• thymo-: thymus
• thyro- / thyroido-: thyroid

Prefixes

• eu-: good, normal
• hyper-: above, excessive
• hypo-: below, deficient
• poly-: many, much

Suffixes

• -al / -ic: pertaining to
• -emia: blood
• -ism: condition of
• -megaly: enlargement
• -oid: resembling
• -osis: abnormal condition
• -penia: deficiency
• -uria: urine, urination

Adjectives and Other Related Terms

• cortical: pertaining to the cortex
• endogenous: produced inside the body
• euthyroid: normal thyroid function
• exogenous: produced outside the body
• metabolism: chemical reactions inside body cells
• pancreatic: pertaining to the pancreas
• postprandial: after a meal
• thymic: pertaining to the thymus

Diabetes

• Diabetes: Means "siphon" or "to pass through."
• Diabetes mellitus: Caused by a deficiency of insulin or the body's inability to respond to insulin, resulting in hyperglycemia (high blood sugar).
• Mellitus means "sweet like honey," referring to the presence of sugar in the urine.
• Diabetes insipidus: Caused by a deficiency of antidiuretic hormone (ADH), leading to excessive urination and thirst.

Types of Diabetes Mellitus

• Type 1 diabetes: An autoimmune disorder where the immune system destroys pancreatic islets, resulting in a total lack of insulin; requires insulin replacement therapy; often called juvenile onset diabetes or early onset diabetes.
• Type 2 diabetes: A condition where body cells become resistant to insulin; often linked to lifestyle factors; can be reversible through diet and exercise; often called adult onset or late onset diabetes.
• Untreated diabetes can lead to catastrophic effects due to lack of nutrition in tissues.

Acidosis

• Acidemia is acidic blood with an abnormally low pH (below 7.4).
• Acidosis is a condition of acidic bodily fluids and tissues
• Diabetic ketoacidosis (DKA): Excessive ketones in the body due to untreated diabetes, where the body uses amino acids or lipids for energy instead of glucose. Acidemia or acidosis can be deadly because body tissues can't function and may not recover from the lack of function.

Endocrine Disorder Terms

• Acromegaly: Enlargement of extremities due to hypersecretion of growth hormone in adulthood.
• Adenitis: Inflammation of a gland.
• Addison's disease: Underactive adrenal gland (hypoactive) resulting in low blood pressure, salt craving, and darkening of the skin.
• Cushing's syndrome: Overactive (hyperactive) adrenal gland resulting in too much cortisol, leading to poor wound healing, abnormal blood pressure, moon face, and fatty deposits.
• Exophthalmos: Protruding or bulging eyes common in Graves' disease (an overactive thyroid disorder and autoimmune disorder) caused by inflammation of the eyes, as well as a long list chronic thyroiditis called Hashimoto's disease where thyroid problems arise.
• Goiter: Enlargement of the thyroid gland.
• Gigantism: Excessive growth hormone during adolescence resulting in abnormally tall stature.
• Hirsutism: Excessive hair growth in women due to a sex hormone imbalance.
• Hyperkalemia: Abnormally high potassium in the blood.
• Hypernatremia: Abnormally high sodium in the blood.
• Hypercalcemia: Abnormally high calcium in the blood.
• Hyperglycemia: Abnormally high sugar in the blood.
• Hypokalemia: Abnormally low potassium in the blood.
• Hyponatremia: Abnormally low sodium in the blood.
• Hypocalcemia: Abnormally low calcium in the blood.
• Hypoglycemia: Abnormally low sugar in the blood.
• Polydipsia: Excessive thirst, commonly seen in diabetes.
• Polyuria: Excessive urination, commonly seen in diabetes.
• Ketosis: Too many ketones in the body, often leading to diabetic ketoacidosis.

Tests and Procedures

Tests for Diabetes

• Fasting blood glucose: Measures blood glucose levels after fasting for at least eight hours.
• Glucose tolerance test: Assesses how the body handles sugar after consuming a sugary drink.
• Glycosylated hemoglobin test (HbA1c): Indicates blood glucose control over a few months; a more accurate measure of diabetes management.

Tests for Thyroid Function

• Radioactive iodine uptake test: Shows the activity level of thyroid tissue.
• Thyroid sonography: Ultrasound of the thyroid to examine its structure.

Surgical interventions

• Pancreatectomy: removal or excision of the pancreas.
• Thyroidectomy: excision of the thyroid.
• Thyroidotomy: incision or cut into the thyroid.