Homeostasis Endocrine System

Diabetes insipidus

• ADH deficiency due to damage to hypothalamus or posterior pituitary

• Must keep well hydrated

Syndrome of inappropriate ADH secretion (SIADH) -

• Retention of fluid, headache, disorientation

  • Fluid restriction; blood sodium level monitoring

Hypersecretion of GH is usually caused by anterior pituitary tumor

• In children results in gigantism

  • Can reach heights of 8 feet

• In adults results in acromegaly

  • Overgrowth of hands, feet, and face

Hyposecretion of GH

• In children results in pituitary dwarfism

  • May reach height of only 4 feet

• In adults usually causes no problems

Hypersecretion of prolactin is more common than hyposecretion

• Hyposecretion not a problem in anyone except women who choose to nurse

• Hyperprolactinemia is the most frequent abnormality of anterior pituitary tumors 

• Clinical signs include inappropriate lactation, lack of menses, infertility in females, and impotence in males

Hyposecretion of TH in adults can lead to

myxedema

• Symptoms include low metabolic rate, thick and/or dry skin, puffy eyes, feeling chilled, constipation, edema, mental sluggishness, lethargy

• If due to lack of iodine, a goiter may develop

  • Lack of iodine decreases TH levels, which triggers increased TSH secretion, triggering thyroid to synthesize more and more unusable thyroglobulin

  • Thyroid enlarges

TH is critical for normal growth and brain development in early childhood

congenital hypothyroidism

• usually caused by poor development of thyroid gland.

  • Pituitary problems or maternal medications may sometimes rarely affect baby’s ability to make TH

  • May be asymptomatic or present with weak cry, poor feeding, constipation or prolonged jaundice

  • TH replacement is crucial and is usually lifelong

Graves’ disease -

• Autoimmune disease: body makes abnormal antibodies directed against thyroid follicular cells

• Antibodies mimic TSH, stimulating TH release

• Symptoms include elevated metabolic rate, sweating, rapid and irregular heartbeats,  nervousness, and weight loss despite adequate food

  • Exophthalmos may result: eyes protrude as tissue behind eyes becomes edematous and fibrous

• Treatments include surgical removal of thyroid or radioactive iodine to destroy active thyroid cells

Hyperparathyroidism due to parathyroid gland tumor -

• Calcium leaches from bones, causing them to soften and deform

• Elevated Ca²⁺ depresses nervous system and contributes to formation of kidney stones

• Osteitis fibrosa cystica: severe form resulting in easily fractured bones

Hypoparathyroidism -

following gland trauma or removal can cause hypocalcemia

• Results in tetany, respiratory paralysis, and death

Aldosteronism;

• hypersecretion usually due to adrenal tumors

  Results in two major problems:

1. Hypertension and edema due to excessive Na⁺

2. Excretion of K⁺, leading to abnormal nonresponsive neurons and muscle 

Hypersecretion—Cushing’s syndrome/disease

• Depresses cartilage/bone formation and immune system; inhibits inflammation; disrupts neural, cardiovascular, and gastrointestinal function

• Causes: tumor on pituitary, lungs, pancreas, kidney, or adrenal cortex; overuse of corticosteroids

• Cushingoid signs: “moon” face and “buffalo hump”

• Treatment: removal of tumor, discontinuation of drugs

Hyposecretion—Addison’s disease -

• Usually involves deficits in both glucocorticoids and mineralocorticoids

• Decrease in plasma glucose and Na⁺ levels

• Weight loss, severe dehydration, and hypotension are common

• Treatment: corticosteroid replacement therapy

• Early sign is characteristic bronzing of skin due to high levels of ACTH which triggers melanin production in melanocytes

Hypersecretion (adrenogenital syndrome (masculinization) -

• Not noticeable in adult males

  • Already masculinized with testosterone, so no effect

• Females and prepubertal males

  • Boys: reproductive organs mature; secondary sex characteristics emerge early

  • Females: beard, masculine pattern of body hair; clitoris resembles small penis

Hyposecretion -

Epinephrine and norepinephrine are not essential to life; therefore there are no problems associated with hyposecretion

Hypersecretion -

• Leads to symptoms of uncontrolled sympathetic nervous system, such as:

  • Hyperglycemia, increased metabolic rate, rapid heartbeat, palpitations, hypertension, intense nervousness, and sweating

• Can be due to pheochromocytoma, tumor of medullary chromaffin cells

Diabetes mellitus (DM) can be due to:

• Hyposecretion of insulin: Type 1

• Hypoactivity of insulin: Type 2

• Three cardinal signs of DM:

  • Polyuria: huge urine output

    • Glucose acts as osmotic diuretic

  • Polydipsia: excessive thirst

    • From water loss due to polyuria

  • Polyphagia: excessive hunger and food consumption

    • Cells cannot take up glucose and are “starving”

When sugars cannot be used as fuel, as in DM, fats are used, causing

lipidemia: high levels of fatty acids in blood

• Fatty acid metabolism results in formation of ketones (ketone bodies) 

• Ketones are acidic, and their build-up in blood can cause ketoacidosis 

  • Also causes ketonuria: ketone bodies in urine

• Untreated ketoacidosis causes hyperpnea, disrupted heart activity and O₂ transport, and severe depression of nervous system that can possibly lead to coma and death 

Hyperinsulinism -

Excessive insulin secretion

• Causes hypoglycemia: low blood glucose levels

• Symptoms: anxiety, nervousness, disorientation, unconsciousness, even death

• Treatment: sugar ingestion

Effects of Environmental Pollutants

• Exposure to pesticides, industrial chemicals, arsenic, dioxin, and soil and water pollutants disrupts hormone function

• Sex hormones, thyroid hormone, glucocorticoids are all vulnerable to effects of pollutants

• Interference with glucocorticoids may help explain high cancer rates in certain areas