Endocrine System Overview

Adrenal Glands

• Produces Mineralocorticoids, Gonadocorticoids, and Glucocorticoids
• Mineralocorticoids: Aldosterone, regulate electrolyte balance
• Gonadocorticoids: Estrogen and Testosterone, influence sexual development
• Glucocorticoids: Cortisol, regulates glucose levels, metabolism, long term stress, and gluconeogenesis

Tropic Hormones

• Tropic hormones target other endocrine glands, stimulating them to produce their own hormones
• Examples:
  • Follicle-stimulating hormone (FSH)
  • Luteinizing hormone (LH)
  • Adrenocorticotropic hormone (ACTH)
  • Thyroid-stimulating hormone (TSH)
  • Growth hormone (GH)
  • Prolactin (PRL)

Diabetes Insipidus vs. Diabetes Mellitus

• Diabetes Insipidus:
  • Normal blood glucose levels
  • Kidneys can't concentrate urine due to low levels of Antidiuretic Hormone (ADH)
  • Symptom: Polyuria (frequent urination)
• Diabetes Mellitus Type 1:
  • Pancreas does not produce insulin
  • Immune system attacks pancreatic beta cells responsible for insulin production
  • Symptom: Polyuria (frequent urination), Polydipsia (excessive thirst)
• Diabetes Mellitus Type 2:
  • Pancreas produces less insulin, or the body becomes resistant to insulin
  • Symptom: Polyuria (frequent urination), Polydipsia (excessive thirst)
  • Potentially reversible
• All three types of diabetes share the symptom of Polyuria (frequent urination)

Exocrine vs. Endocrine Glands

• Exocrine glands: Secrete substances into a ductal system that leads to an epithelial tissue outside the body
• Endocrine glands: Secrete products directly into the bloodstream

Prostaglandins

• Affect several bodily functions, including inflammation and pain

Hormone Mechanisms of Activation

• Protein Hormones:
  • Bind to receptors on the cell surface
  • Activate G-protein
  • Activate Adenylcyclase (enzyme)
  • Catalyze ATP conversion to cAMP (second messenger)
  • cAMP activates Protein Kinase
  • Relatively rapid action
• Steroid Hormones:
  • Enter the cell
  • Bind to receptors in the nucleus
  • Activate new genes
  • New proteins are synthesized
  • Relatively slow action

Positive vs. Negative Feedback

• Negative Feedback: Prevents excessive response to a stimulus
• Positive Feedback: Intensifies the response until an endpoint is reached

Thyroid Hormone

• Thyroid Hormone controls metabolism, growth, and other bodily functions
• Two forms:
  • Triiodothyronine (T3)
  • Thyroxine (T4)

Cretinism and Pituitary Dwarfism

• Cretinism: Caused by maternal hypothyroidism, often due to iodine deficiency
• Pituitary Dwarfism:
  • Caused by brain tumors, diseases affecting pituitary or hypothalamus
  • Head trauma, radiation therapy, or autoimmune conditions like lymphocytic hypophysitis
  • Reduced Growth Hormone (GH)

Hyperthyroidism vs. Hypothyroidism

• Hyperthyroidism:
  • Thyroid gland produces too much thyroid hormone
  • Symptoms: muscle weakness, trouble sleeping, irregular heartbeat, etc.
  • Exophthalmos (bulging of the eyes)
• Hypothyroidism:
  • Thyroid gland produces too little thyroid hormone
  • Symptoms: fatigue, weight gain, joint/muscle pain, puffy face, etc.

PTH, Calcitonin, Glucagon, and Insulin

• Parathyroid Hormone (PTH): Levels are controlled by a feedback loop based on calcium levels in the blood
• Calcitonin: Thyroid gland releases Calcitonin based on calcium levels in the blood. High calcium levels trigger release, lowering calcium levels.
• Glucagon: Released based on circulating glucose levels, increasing glucose levels
• Insulin: Released based on plasma glucose concentration, decreasing glucose levels when high

Gluconeogenesis

• Process of generating glucose from breakdown products of lipids, proteins, or its original components
• Occurs when glucose supply is low

Hypothalamus and Pituitary Gland

• Hypothalamus: Controls secretions of the Adenohypophysis (anterior pituitary)
• Neurohypophysis (posterior pituitary): Structural foundation for neurohumoral system coordinating fluid balance and reproductive function

Ketoacidosis

• Occurs when blood becomes acidic due to high ketone levels
• Caused by a lack of insulin (characteristic of Type 1 Diabetes)
• Leads to Metabolic Acidosis