ENDOCRINE

• Endocrine system


  Collection of glands that secrete hormones
• Endocrine system


  • Hormones travel through the bloodstreams to the target organs
  • Signaling pathway (chemical messengers)
  • Slower than nerve impulses
  • Few hours to few weeks
  • Main control center is the HYPOTHALAMUS in the brain
• Types of signaling in the endocrine system

  • Autocrine
  • Paracrine
  • Neurotransmitter
  • Endocrine
• Endocrine organs


  • Hypothalamus
  • Pituitary gland
  • Pineal gland
  • Thyroid gland
  • Parathyroid gland
  • Enteric endocrine system (pancreas & GI tract)
  • Suprarenal (adrenal) glands
  • Testes and ovaries
  • Thymus
• Characteristics of hormones


  • Stability depends on composition (lipid-soluble vs water-soluble, amino acid derivatives or steroid hormones)
  • Interacts with target tissues
  • Wide distribution
  • Mode of release: chronic, acute, episodic
• Hypothalamus


  Almond-sized structure in the limbic system that controls the endocrine system (releases or inhibits hormones, thus, neurohormones)
• Hypothalamus


  1. Direct projections to the posterior pituitary (neurohypophysis)

  2. Indirect control over the anterior pituitary (adenohypophysis)

  3. Projections into the median eminence

  4. Autonomic nervous system
• Hormones produced by the hypothalamus

  • Anti-diuretic hormone (ADH)
  • Corticotropin-releasing hormone (CRH)
  • Gonadotropin-releasing hormone (GnRH)
  • Growth hormone-releasing hormone (GHRH) or growth hormone-inhibiting hormone (GHIH)
  • Oxytocin
  • Prolactin-releasing hormone (PRH) or prolactin-inhibiting hormone (PIH)
  • Thyrotropin releasing hormone (TRH)
• Pathologies related to the hypothalamus

  • Diabetes Insipidus
  • Prader-Willi syndrome
  • Hypopituitarism
  • Gigantism
  • Acromegaly
• Pituitary gland


  Hypophysis cerebri, pea-sized, ovoid shaped structure that stores some of the hormones that the hypothalamus produces before releasing into the blood
• Hormones produced by the anterior pituitary

  • Human-growth hormone (hGH)
  • Thyroid-stimulating hormone (TSH)
  • Follicle-stimulating hormone (FSH)
  • Luteinizing hormone (LH)
  • Prolactin (PRL)
  • Adrenocorticotropic hormone (ACTH)
  • Melanocyte-stimulating hormone (MSH)
• Pathologies related to the pituitary gland

  • Cushing's syndrome
  • Prolactinoma
  • Hypopituitarism
  • Sheehan's syndrome
  • Diabetes insipidus
  • Rathke's cleft cyst
  • Hypophysitis
• Pineal gland


  Epiphysis cerebri, small organ located in a depression between the superior colliculi, inferior to the splenium of the corpus collosum
• Melatonin


  Hormone released from the pineal gland that is involved in sexual development, sleep-wake cycle
• Pathologies related to the pineal gland

  • Depression
  • Mood swings
  • Peptic or stomach ulcers
  • Disruption of sleep patterns
  • Hormonal imbalance
  • Sexual disorders
• Thyroid gland


  Located at the base of the neck, anterior portion of the neck at the level of the C5-T1 vertebrae deep to the sternothyroid and sternohyoid muscles
• Thyroxine (T4) and Triiodothyronine (T3)


  Hormones produced by the thyroid gland that affect the body's metabolism
• Calcitonin


  Hormone produced by the thyroid gland that is an antagonist of the parathyroid hormone
• Pathologies related to the thyroid gland

  • Hyperthyroidism
  • Hypothyroidism
  • Hashimoto's thyroiditis
  • Grave's disease
  • Goiter
  • Thyroid nodules
• Parathyroid glands


  Small, flattened, and oval structures located on the posterior surface of each lobe of the thyroid gland that maintain calcium levels by producing parathyroid hormone
• Pathologies related to the parathyroid glands

  • Hyperparathyroidism
  • Hypoparathyroidism
  • Parathyroid cancer
• Enteric endocrine system


  Includes the pancreas and gastrointestinal tract, produces hormones in response to the environment instead of continuously
• Insulin


  Hormone produced by the beta cells of the Islets of Langerhans in the pancreas that promotes absorption of glucose from the blood into liver, fat, and skeletal muscle cells
• Glucagon


  Hormone produced by the pancreas that increases blood sugar level and prevents it from dipping too low
• Hormones produced by the gastrointestinal tract

  • Gastrin
  • Secretin
  • Ghrelin
  • Motilin
  • Cholecystokinin
  • Gastric inhibitory polypeptide
• Zollinger-Ellison syndrome is a pathology related to the enteric endocrine system
• Adrenal glands


  Triangular shaped glands on top of the kidneys (thus, suprarenal glands), with a cortex that produces glucocorticoids and a medulla that produces adrenaline and noradrenaline
• Pathologies related to the adrenal glands

  • Addison's disease
  • Cushing's syndrome
  • Aldosterone-producing adenomas
  • Adrenocortical carcinoma
  • Pheochromocytoma
• Ovaries


  Paired, almond-shaped glands that produce oocytes and female hormones
• Testes


  Paired, ovoid glands that produce spermatozoa and testosterone
• Estrogen and Progesterone


  Hormones produced by the ovaries as a result of LH and FSH production, involved in sexual development, reproduction, and regulation of the menstrual cycle
• Pathologies related to the female reproductive glands

  • Ovarian cancer
  • Ovarian cysts
  • Primary ovarian insufficiency
  • Ovarian torsion
  • PCOS
• Pathologies related to the male reproductive glands

  • Hypogonadism
  • Klinefelter syndrome
  • Infertility
  • Testicular trauma
  • Testicular torsion
  • Testicular cancer
  • Epididymitis
  • Cryptorchidism
  • Polyorchidism
  • Tranverse testicular ectopia
• Thymus


  Located behind the breastbone and between the lungs, shrinks as you age, involved in T cell production and hormone production
• Hormones produced by the thymus

  • Thymopoietin
  • Thymulin
  • Thymosin
  • Thymic humoral factor
• Pathologies related to the thymus

  • DiGeorge syndrome
  • Thymic hyperplasia
  • Thymic cysts
  • Tumors of the thymus
  • Myasthenia gravis, pure red cell aplasia, hypogammaglobulinemia, thymoma-associated multiorgan autoimmunity
• Remember: Humoral, neural, hormonal stimuli and inhibition, treatment of the gland itself, agonist and antagonist, negative feedback and positive feedback, receptor number of target tissues
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