Untitled Quiz

Composed of adrenal medulla and adrenal cortex
Adrenal cortex is divided into three zones: glomerulosa, fasciculata, and reticularis
Zona glomerulosa produces mineralocorticoids (e.g., aldosterone), regulating salt and water balance
Zona fasciculata synthesizes glucocorticoids (e.g., cortisol), involved in metabolism and stress response
Zona reticularis secretes adrenal androgens (e.g., dehydroepiandrosterone)

Aldosterone accounts for 90% of mineralocorticoid activity
Primary function: regulates electrolytes by increasing sodium reabsorption and potassium excretion
Mechanisms:
- Kidney: Increases sodium reabsorption and potassium excretion mainly in the collecting tubules and to a lesser extent in the distal tubules and collecting ducts
- Intestine: Increases sodium absorption mainly in the colon to prevent sodium loss in stool
- Sweat and salivary glands: Increases sodium chloride reabsorption and potassium secretion
Regulation of extracellular fluid and arterial blood pressure
- Sodium reabsorption by renal tubules stimulates osmotic reabsorption of water
- Excess aldosterone increases extracellular fluid volume and blood pressure

Increased potassium ion concentration in the blood increases aldosterone secretion
Increased activity of the renin-angiotensin system increases aldosterone secretion (often due to decreased blood flow to the kidneys)
Decreased sodium ion concentration in the blood increases aldosterone secretion
ACTH has a permissive effect on aldosterone secretion

In humans, cortisol is the primary glucocorticoid
Functions of cortisol:
- Carbohydrate metabolism: Increases gluconeogenesis in the liver (conversion of amino acids to glucose) and decreases glucose uptake by tissues
Protein metabolism: Increases protein catabolism in extrahepatic tissues(muscle) and decreases protein synthesis; increases amino acid transport to the liver and formation of plasma proteins
Fat metabolism: Increases lipolysis in adipose tissues and increases fatty acid oxidation

Hypothalamus secretes corticotrophin-releasing hormone (CRH) which stimulates the anterior pituitary to release ACTH which stimulates cortisol secretion
Cortisol produces negative feedback inhibition on the hypothalamus and anterior pituitary
Physical or mental stress greatly enhances the secretion of ACTH and cortisol
Circadian rhythm: Cortisol secretion is high in the early morning but low in the late evening

Causes: Overproduction of aldosterone, often due to tumors of the zona glomerulosa
Manifestations:
- Sodium retention, leading to hypertension
- Potassium loss, leading to hypokalemia (muscle weakness and cardiac arrhythmias)
- Alkalosis (due to H+ loss in urine)
Edema may not develop due to the escape phenomenon—Increased extracellular fluid will trigger secretion of atrial natriuretic factor, resulting in Na+ excretion

Causes: Excess cortisol secretion, possibly due to
- Primary hyperfunction: tumor of the adrenal gland
- Secondary hyperfunction: increased ACTH output from a pituitary tumor, or from prolonged steroid administration
Manifestations:
- Hypertension
- Hyperglycemia and diabetes
- Moon face, buffalo hump, and truncal obesity
- Muscle weakness
- Osteoporosis
- Thinning of the skin and striae (stretch marks)

Primary adrenal insufficiency (Addison's disease): Causes:
- Atrophy of the adrenal cortex
- Destruction of the adrenal cortex (e.g., by cancer or autoimmune disease)
Manifestations:
- Lack of aldosterone: Sodium levels decrease, potassium levels rise, severe dehydration, and hypotension
- Lack of cortisol: Decreases blood glucose, decrease resistance to stress, and skin pigmentation

Mixed gland (exocrine and endocrine functions)
Exocrine function: Secretes digestive enzymes (pancreatic juices) into the digestive tract
Endocrine function: Secretes hormones regulating blood sugar levels; located in islets of Langerhans
Islets of Langerhans contain different cell types
- Beta cells: Secrete insulin
- Alpha cells: Secrete glucagon
- Delta cells: Secrete somatostatin

Peptide hormone secreted by beta cells of pancreatic islets of Langerhans
Maintains normal blood glucose levels by facilitating cellular glucose uptake
Regulates carbohydrate, lipid, and protein metabolism
- Increases glycogen, fatty acid, and triglyceride formation in the liver
- Stimulates glucose uptake by muscle and adipose tissue
- Decreases blood glucose concentration

"Fasted state" hormone working with insulin to maintain blood glucose homeostasis in the blood
Secreted by alpha cells in the pancreas
Increases blood glucose concentration by stimulating glycogenolysis. Glycogen conversion (stored in liver) into glucose is released into the bloodstream.
Stimulates gluconeogenesis

Characterized as an inability for the body to produce enough insulin, or a decreased response to insulin in target tissues.
Marked by elevated blood glucose levels
Two forms:
- Type 1 (insulin-dependent): absolute deficiency of insulin due to autoimmune disease that destroys beta cells (usually diagnosed in younger age groups)
- Type 2 (non-insulin-dependent): characterized by decreased tissue sensitivity to insulin. (most common form, usually diagnosed in older age groups, often linked to obesity)

Blood sugar levels are higher than normal, but not high enough to be diagnosed as diabetes
Fasting blood glucose levels: 100 mg/dL - 125 mg/dL
Oral glucose tolerance test (OGTT): 140 mg/dL - 199 mg/dL

Fasting blood glucose levels of 126 mg/dL or higher
Random blood glucose level over 200 mg/dL
Glycosylated hemoglobin (A1C) levels of 6.5% or higher indicate diabetes. 5.7-6.4% indicates prediabetes.