Endocrine System

What is the endocrine system?

Consists of ductless glands that secrete chemical messengers called hormones directly into the bloodstream to regulate distant target organs

What is the pituitary gland?

Pea sized organ located at the base of the brain, connected to hypothalamus by stalk called infundibulum

What are the parts of the pituitary gland?

Anterior lobe (adenohypophysis) and posterior lobe (neurohypophysis)

What other glands are part of the endocrine system?

Thyroid, parathyroid, adrenal, gonads

Where are secondary endocrine tissues?

Heart, stomach, intestines, kidneys, thymus

What do endocrine hormones do?

Affect widespread body functions like growth, development, metabolism, muscle and fat distribution, sexual development, fluid and electrolyte balance, inflammation, immune response

What do hormones affect?

Some affect the whole body, while others act only on specific target organs

What are hormones made of?

Either proteins or steroids derived from cholesterol

What does the pituitary gland do and what is it regulated by?

Control most glandular activity, regulated by hypothalamus to maintain homeostasis and is part of the central nervous system

How does the body control hormone circulation?

Via negative feedback mechanisms — when circulating hormone levels are adequate, further release is stopped

How do insulin and glucagon work?

Insulin is secreted when blood sugar rises, glucagon acts antagonistically to insulin and is released when blood sugar levels fall below normal

What physical evaluations are used for the endocrine system?

Only thyroid and testes via palpation

What are immunoassays?

ELISA and RIA, hormone levels measured in blood or urine samples using Enzyme Linked Immunosorbent Assay, or Radioimmunoassay

What occupies antibody binding sites?

Labelled hormones in the sample compete with unlabelled hormones for limited number of antibody binding sites

What can be found in High Sample Hormone Concentration?

Most of the resulting antigen antibody complexes will be unlabelled?

What can be found in Low Sample Hormone Concentration?

Most of the antigen-antibody complexes will be labelled

How can imaging and histological tests be used for the endocrine system?

Imaging tests to locate glandular tumors, biopsy taken to determine if a tumor is malignant

What hormones are produces by the anterior pituitary?

GH, TSH, Prolactin, ACTH, FSH, LH

What is GH and it’s primary physiological action?

Growth Hormone, promotes growth of tissues and bones across all body parts, pre puberty it stimulates long bone growth and soft tissues but post puberty it is secreted in lesser amounts but helps with tissue replacement and repair

What is TSH and it’s primary physiological action?

Thyroid Stimulating Hormone, controls hormone secretion by the thyroid gland, without it the thyroid stops functioning entirely

What is Prolactin and it’s primary physiological action?

Stimulates breast development and milk synthesis during pregnancy and after delivery

What is ACTH and it’s primary physiological action?

Adrenocorticotropic Hormone, stimulates release of hormones from outer part of the adrenal glands

What is FSH and it’s primary physiological action?

Follicle Stimulating Hormone, regulates sexual development and functions, stimulates egg and sperm production

What is LH?

Luteinizing hormone, stimulates ovaries to produce estrogen/progesterone and testes to produce testosterone, acute surge triggers ovulation

How are hormones stored in the Posterior Pituitary?

Produced in the hypothalamus then stored in the posterior pituitary, connected to the hypothalamus by a stalk called the infundibulum

What hormones does the posterior pituitary produce?

ADH and Oxytocin

What is ADH?

Antidiuretic hormone/vasopressin, stimulates water reabsorption in the kidneys having an antidiuretic effect (reducing urine production)

What is oxytocin?

Stimulates uterine contractions during labor and triggers breast milk release in response to suckling, in males causes ejection of prostate gland secretions

What is the thyroid gland?

Located in the neck, one lobe on either side of trachea, connected by an isthmus anterior to the trachea

What hormones does the thyroid gland produce?

TH: Thyroxine T4 and Triiodothyronine T3, calcitonin

What is TH?

Thyroxine T4 or Triiodothyronine T3, iodine containing hormones that affect whole body by increasing metabolism, principle form is T4, small amount of T3 is produced directly but most T3 is formed by converting T4

What is calcitonin?

Decreases blood calcium levels and increases bone mass

What are the parathyroid glands?

Four tiny glands located behind the thyroid?

What hormones do the parathyroid glands produce?

PTH (parathyroid hormone)

What is parathyroid hormone?

Increases blood calcium via renal absorption instead of urine, increasing intestinal absorption and osteoclast activity to break down bone

Why is calcium in blood?

99% of calcium is in bone, the 1% in blood is essential for clotting, nerve conduction, and muscle contraction

What is the adrenal cortex?

Outer glandular region of the adrenal gland, sits on top of each kidney, stimulated by ACTH

What hormones does the adrenal cortex make?

Mineralocorticoids, glucocorticoids, sex hormones

What are Mineralocorticoids?

Regulates salt balance, causes sodium retention and potassium secretion by the kidneys

What are Glucocorticoids?

Regulates carbohydrate, lipid, and protein metabolsim

What are sex hormones?

Secretes androgens in males and estrogens in females

What is the adrenal medulla?

Inner layer, secretes in stress situations

What hormones does the adrenal medulla produce?

Epinephrine, norepinephrine

What is epinephrine?

Causes vasodilation, increasing heart rate, blood pressure, respiration

What is norepinephrine?

Causes general vasoconstriction

How do epinephrine and norepinephrine help the body?

Provides additional strength and energy, together they shunt blood to vital organs

What is the endocrine pancreas?

Fish shaped organ lying across the middle of the abdominal cavity below stomach, divided into head body and tail, holds endocrine and exocrine functions

What hormones does the endocrine pancreas produce?

Insulin, glucagon, somatostatin

What is insulin?

Secreted by beta cells, located in patches of tissue called islets of Langerhans when blood sugar rises, moves glucose out of blood and into tissues

How are excess carbs stored?

As glycogen in the liver

Normal glucose range?

80-120 mg/dL

What is glucagon?

Secreted by alpha cells of islets when blood sugar drops, stimulates liver to release glycogen in form of glucose to raise blood sugar

What is somatostatin?

Secreted by delta cells directly inhibited both insulin and glucagon secretion

What are gonads?

Primary reproductive glands and sex organs (testes for males ovaries for females)

What hormones are produced by gonads?

Estrogen and progesterone by ovaries and testosterone by testes

What are ovaries?

Function as endocrine glands and source of ova, regulate sexual development, secondary sex characteristics, and female reproductive cycle

What are testes?

Function as endocrine glands and source of sperm, regulate sexual development and secondary sex characteristics in males

What is the the pathophysiology of pituitary dwarfism?

Inadequate secretion of growth hormone by anterior pituitary in children causing growth impairment throughout childhood, normal puberty may or may not occur depending on the degree to which pituitary can produce other hormones

What is the etiology of pituitary dwarfism?

Inherited disorders, malignant tumors, inadequate secretion of hormones, inflammation, radiation, vascular changes of the pituitary resulting in hyposecretion

Diagnosis for pituitary dwarfism?

Blood test confirming low GH alongside imaging tests

Treatment for pituitary dwarfism?

GH replacement therapy

What is anterior pituitary hypersecretion in children?

Gigantism, hypersecretion of GH in children before growth plates close, exceptionally rare with only 100 cases reported to date

Etiology of gigantism?

Most commonly caused by benign tumor of pituitary gland leading to excessive secretion of GH, prevention not possible

Signs and symptoms of gigantism?

Facial features thicken, hands and feet bigger than normal, headaches, excess sweating, late onset puberty, joint problems, cardiovascular weakness, myopathy, shorter life expectancy

Diagnosis for anterior pituitary hypersecretion in children?

Physical exam, imaging tests, biopsy, blood test confirming high GH

Surgical and surgical related treatments of anterior pituitary hypersecretion in children?

Surgical tumor removal in cases of well defined tumors, radiation may be used in conjunction with surgery or where surgery not possible

Other treatments for gigantism?

Medications to reduce growth hormone secretion where surgery not feasible

What is anterior pituitary hypersecretion in adults?

Acromegaly, excess GH secretion during adulthood, growth plates are closed so long bones do not grow

Onset and prevalence of acromegaly?

Insidious onset, symptoms usually present for years before diagnosis, prevalence 4676 cases per million with no risk factors

Etiology of acromegaly?

Benign tumor of pituitary gland leading to excessive secretion of GH

Signs and symptoms of acromegaly?

Big hands, feet, and head, soft tissue thickening of palms of hands and soles of feet, enlargement of jaw causes teeth to spread, enlargement of tongue, arthritis

What is the diagnostic procedure for acromegaly?

Based on medical history, physical exam, blood tests confirming high GH, imaging tests, biopsy

Treatment for acromegaly?

Surgically removing tumors of pituitary or hypothalamus, shrinking with radiation and meds that decrease GH

What is the ancient history for diabetes?

Signs were recorded in ancient Hindu writings thousands of years ago noting a large volume of urine that attracted ants because of sugar, intense thirst, wasting of body

What was the 19th century breakthrough for diabetes?

Definitely linked to pancreas when observed in dogs whose pancreas had been experimentally removed

How did diabetes treatment evolve over time?

The hormone insulin was later isolated and identified as a diabetes treatment, today it is synthesized from bacteria using recombinant DNA technology

Modern outlook for diabetes?

Early diagnosis, treatment, effective management have lengthened and greatly improved lives of diabetics, still no cure tho

What is Posterior Pituitary Hyposecretion?

Diabetes insipidus, decreased secretion of ADH (vasopressin)

Incidence of DI?

3/100000

Clinical presentation of diabetes insipidus?

Production of abnormally large amounts of urine (polyuria), extreme thirst and increase in fluid intake (polydipsia), increased urinary frequency, disturbed sleep and daytime fatigue, weight loss, low blood pressure

What is the underlying etiology of central DI?

Caused by damage to pituitary from surgery, tumor, illness, or injury

What is the underlying etiology of nephrogenic DI?

Caused by defect in kidney tubules, making kidneys unable to properly respond to ADH, or the use of certain drugs such as lithium and demeclocycline

Diagnostic procedure for DI?

Medical history, physical exam, urinalysis showing colourless urine with low specific gravity, water restriction test, water intake reduced for several hours while measuring urine output, blood pressure, and urine concentration

What is the confirmatory evaluation for DI?

If patient is later given vasopressin medication and it successfully decreases urine output and increases concentration, central DI diagnosis is confirmed

Treatment for DI?

Aimed at removing primary cause and treating symptoms to prevent dehydration, vasopressin as nasal or tablet for central, compensatory fluid for nephrogenic but dialysis or transplant may be needed for severe cases

What is Hypoadrenalism?

Addison’s disease, primary adrenal insufficiency presenting as undersecretion of hormones by adrenal cortex

What are the symptoms of Addison’s disease associated with?

Destruction of adrenal glands were first described in 1855 by Thomas Addison

Prevalence of Addison’s Disease?

1/1000, twice as common in females and usually diagnosed between ages 30 to 60, not preventable

Etiology of Addison’s Disease?

Caused by disease processes that damage adrenal cortex, 75-80% of cases are due to autoimmune processes

What are some other causes of Addison’s Disease?

Infectious disease, opportunistic infections associated with AIDS, certain cancers, hemorrhage of adrenal gland due to anticoagulation medication

Signs and symptoms of Addison’s Disease?

Weight loss, anorexia, abdominal discomfort, vomiting, diarrhea, fatigue, dizziness, fainting due to fluid loss and hypotension, characterized by hyperpigmentation in non sun exposed areas

Diagnosis of Addison’s Disease?

Medical history, physical exam, blood tests confirming low cortisol and high ACTH, verified via ACTH simulation test measuring cortisol level before and after an ACTH injection and imaging tests

Treatment for Addison’s Disease?

Lifelong replacement of both glucocorticoids and mineralocorticoids, during stress, patients may need additional meds such as hydrocortisone due to lack of cortisol

What is Acute Adrenal Insufficiency?

Addisonian Crisis, life threatening condition occurring in patients with Addison’s disease who also have other acute illnesses such as infection, trauma, severe physical stress such as surgery

What are the signs and symptoms of Addisonian Crisis?

Symptoms develop rapidly and include nausea, vomiting, abdominal pain, severe hypotension, death can result from shock and cardiovascular collapse

Treatment for Addisonian Crisis?

Immediate rehydration with saline solution and iv glucocorticoid replacement

Primary hormonal issue for Cushing’s Syndrome?

Cortisol overproduction?

Prevalence of Cushing’s Syndrome?

Prevalence of approximately 1 in every 500 000 people

Etiology of Cushing’s Syndrome?

Often caused by benign pituitary tumor, adrenal tumors that cause excessive secretion of cortisol, or prolonged administration of large doses of cortisone

Key clinical presentation of Cushing’s Syndrome?

Fat accumulation behind shoulders known as buffalo hump, round moon shaped face, stretch marks on skin, fatigue and weakness, impaired wound healing and easy bruising, weight gain and protruding abdomen, hypertension