Cortisol regulation

• These are study notes on cortisol regulation, cushing's disease, diabetes mellitus, pancreas, and thyroid and parathyroid

Cortisol Regulation

• Hypothalamus releases CRH, which stimulates the anterior pituitary.
• Anterior pituitary releases ACTH, which stimulates the adrenal cortex.
• Adrenal cortex releases cortisol.
• Cortisol provides negative feedback, inhibiting CRH and ACTH production.

Cushing's Disease

• Cushing's disease involves prolonged exposure to high levels of cortisol.
• The most common cause is a tumor in the pituitary gland.
• Moon face refers to a rounded, full face.
• Buffalo hump is fat accumulation on the back of the neck and upper back.
• Central obesity is fat concentrated in the abdomen with thin limbs.
• Striae are wide, purple or reddish stretch marks, often on the abdomen, thighs, or breasts.
• Thinning skin means there is increased fragility of the skin, leading to easy bruising and slow wound healing.
• Excessive hair growth (hirsutism) is facial or body hair growth, especially in women.
• Metabolic effects include hyperglycemia, which is elevated blood sugar levels due to increased gluconeogenesis.
• Muscle wasting involves weakness due to protein catabolism.
• Bone loss involves osteoporosis and an increased risk of fractures.

Diabetes Mellitus

• Diabetes mellitus reduces glucose uptake into cells, leading to high blood sugar.
• Type 1 diabetes occurs when the pancreas can't produce insulin due to damaged beta cells, often starting around age 14 (juvenile diabetes).
• The cause of beta cell damage in type 1 diabetes is not well understood.
• Type II diabetes occurs when cells don't respond properly to insulin, usually developing around age 45 but increasingly seen in younger people.
• Type II diabetes is linked to diet, lifestyle, and genetics, and can lead to beta cell exhaustion and reduced insulin production.
• "Diabetes mellitus" means "honey-sweet diabetes" because of the sweet-smelling urine caused by high glucose levels.
• Polyuria is increased urination, with glucose in fluid that becomes urine
• Thirst means decreased reabsorption of water makes the body dehydrated
• Increased blood glucose can lead to damage of blood vessels
• Metabolic acidosis can deplete other energy sources since glucose is not used properly
• Sudden weight loss and the breakdown of fats releases ketones, making the pH of the body more acidic.

Pancreas

• The pancreas produces and secretes hormones that regulate blood sugar levels (insulin and glucagon).
• Insulin lowers blood sugar by helping cells take in glucose, while glucagon raises blood sugar by signaling the liver to release stored glucose.
• Type I diabetes is when the pancreas fails to produce enough insulin
• Type 2 diabetes occurs when the body's cells become resistant to insulin
• The pancreas contains both endocrine tissue, it secretes hormones, and exocrine tissue, which secretes chemicals through a duct into the digestive tract
• The endocrine part of the pancreas has 1-2 million islets with three main cell types: alpha cells (25%) release glucagon, beta cells (60%) release insulin and amylin, and delta cells (10%) release somatostatin.
• The exocrine part contains pancreatic acinar cells and ducts.
• Glucagon is released in response to low blood glucose or a fasted state.
• Glucagon acts on tissues and stimulates production and release of glucose from storage.
• Muscle cells with glucagon release glycogen
• Glucagon is a peptide hormone
• Insulin responds to high blood glucose or the fed state.
• Insulin is secreted by pancreas and released into the blood stream
• Insulin promotes movement of glucose from blood to inside target tissue cell.
• Insulin is a peptide hormone.
• A rise in blood glucose stimulates insulin secretion from beta cells.
• A drop in blood glucose or increase in amino acid levels stimulates glucagon secretion from alpha cells
• Insulin promotes movement of glucose into certain cells and stimulates formation of glycogen from glucose
• In response to insulin, blood glucose drops toward normal (and inhibits insulin secretion)
• Glucagon stimulates cells to break down glycogen into glucose (glycogenolysis) and to convert noncarbohydrates into glucose (gluconeogenesis)
• In response to glucagon, blood glucose rises toward normal and inhibits glucagon secretion

Thyroid and Parathyroid

• The thyroid gland, located in the neck, produces the hormones triiodothyronine (T3) and thyroxine (T4), which regulate metabolism, energy production, and growth.
• T4 (thyroxine) is the inactive form, converted into T3 in tissues when needed.
• T3 (triiodothyronine) is the active form that increases metabolic rate, heart function, body temperature, and other activity.
• These hormones are controlled by the hypothalamic-pituitary-thyroid (HPT) axis, and their levels are regulated by a negative feedback loop to maintain balance.
• Parafollicular cells release calcitonin when blood calcium levels are too high, reducing bone resorption, increasing calcium excretion in urine, and decreasing intestinal calcium absorption.
• This helps maintain calcium balance, working in opposition to PTH.
• Hypothalamus releases TRH, which stimulates the pituitary.
• Pituitary releases TSH, which stimulates the thyroid.
• Thyroid produces T3 and T4
• T3 affects metabolism, heart rate, and energy levels.
• T3 (active hormone) regulates body functions, while T4 serves as a reservoir.
• Negative feedback keeps hormone levels balanced.

Study notes on cortisol regulation, Cushing's disease, diabetes mellitus, pancreas, and thyroid and parathyroid. Cortisol regulation includes the release of hormones from the hypothalamus, anterior pituitary, and adrenal cortex. Cushing's disease involves high cortisol levels, often due to a pituitary tumor, leading to symptoms like moon face and central obesity.