Week 1

• • Proteins/polypeptides are made in the RER and can be water-soluble
  • steroids are derived from cholesterol and are generally water-insoluble
• Functions of hormone-binding proteins

  • increases solubility
  • acts as a circulating hormone reservoirs
  • protects active hormones
  • presents active hormones to target cells
• Hormone categories

  • Peptide/protein - made of amino acid chain.
  • Biological amine - made of a single amino acid.
  • Steroid - made of cholesterol.

  
• Autocrine vs paracrine vs endocrine signaling

  • Autocrine - cell targets itself.
  • Paracrine - cell targets nearby cell(s).
  • Endocrine - cell targets distant cell(s) through the bloodstream.

  
• Endocrine vs neural signaling

  
• Examples of hormone-binding proteins

  • cortisol binding globulin
  • thyroid hormone binding globulin
  • sex hormone-binding globulin
  • vitamin D binding protein
  • IGF binding protein
• The hypothalamus produces releasing and inhibiting hormones that act on the pituitary gland, which then releases pituitary hormones.
• Hormones are part of regulatory hormonal cascades involving the hypothalamus, pituitary gland, and target glands.
• Hormones control the growth, development, metabolism, electrolyte composition, and reproduction of the body.
• Hormones are molecules produced by endocrine glands and released into the bloodstream in response to specific stimuli.

  
  

  Hormones are carried via the blood to their target cells, which have specific receptors for the hormone.

  
  

  Hormones can trigger biochemical reactions in target cells, modifying their function or activity.
• Hormones can be classified into different classes, including steroids, amino acid derivatives, and polypeptides/proteins, based on their molecular structures.
• Steroids can enter target cells and interact with receptors in the cytoplasm or cell nucleus, regulating the activity of specific genes.
• Amino acid derivatives can also enter cells and interact with receptor proteins associated with specific DNA regions, modifying gene activity.
• Polypeptide and protein hormones cannot enter cells and instead interact with receptors on the cell surface, initiating biochemical changes that modify cell activity.
• Short-loop feedback can occur, where pituitary hormones directly act back on the hypothalamus.

  
  

  Sensitivity of negative feedback systems can change at different physiological states or stages of life.
• Positive feedback mechanisms exist, where a target gland hormone acts back on the hypothalamus and/or pituitary to increase the release of hormones that stimulate the secretion of the target gland hormone.
• Hypothalamic hormones are released into blood vessels that connect the hypothalamus and the pituitary gland through the hypothalamic-hypophyseal portal system.
• Major releasing and inhibiting hormones from the hypothalamus include corticotropin-releasing hormone (CRH), gonadotropin-releasing hormone (GnRH), thyrotropin-releasing hormone (TRH), growth hormone-releasing hormone (GHRH), somatostatin, and dopamine.
• GH modulates the activities of numerous target organs, including the liver, kidneys, bone, cartilage, skeletal muscle, and adipose cells.

  
  

  GH plays a pivotal role in controlling the body's growth and development and also affects carbohydrate, protein, and fat metabolism.
• Insulin-like growth factor 1 (IGF-1): Produced in the liver and kidneys, transported in the blood to target organs where it stimulates DNA production and cell division for growth.
• Growth hormone (GH): Controlled by hypothalamic hormones (GHRH and somatostatin), released in response to stress, low blood sugar levels, exercise, and deep sleep.

  
  

  Alcohol consumption reduces GH and IGF-1 levels.
• Prolactin: Plays a role in breast development and lactation. Controlled by estrogen levels during pregnancy and suckling in nursing women.

  
  

  Alcohol consumption can affect prolactin release and milk production.
• Vasopressin: Regulates water and electrolyte balance. Release is controlled by sodium concentration, blood volume, and blood pressure. Alcohol inhibits vasopressin release.
• Oxytocin: Stimulates uterine contractions during childbirth and milk ejection in nursing women.

  
  

  Alcohol consumption can affect oxytocin release.
• Adrenal glands: Cortex produces corticosteroids and small amounts of sex hormones.

  
  

  Medulla produces adrenaline and noradrenaline as part of the fight-or-flight response.

  
  

  Cortisol, a glucocorticoid, regulates carbohydrate, protein, and lipid metabolism.
• Cortisol:

  
  

  Promotes protein and lipid breakdown into amino acids and glycerol for gluconeogenesis and protects the body against the effects of stress factors

  
  

  High levels of cortisol can be fatal for individuals without the ability to decrease cortisol levels

  
  

  High doses of cortisol can be used medically to suppress tissue inflammation and reduce immune response
• Aldosterone:

  
  

  Regulates water and electrolyte balance in the body

  
  

  Functions to conserve sodium and excrete potassium

  
  

  Promotes reabsorption of sodium in the kidney, reducing water excretion and increasing blood volume

  
  

  Prevents sodium loss through sweat and saliva
• Gonads and Sex Hormones:

  
  

  Gonads (ovaries and testes) produce germ cells and synthesize steroid sex hormones

  
  

  Three types of sex hormones: estrogens, progestogens, and androgens

  
  

  Estrogens, such as estradiol, coordinate the development and functioning of female genitalia and breasts, regulate menstrual cycle, and maintain female libido

  
  

  Reduction in estrogen levels during menopause leads to symptoms like hot flashes, osteoporosis, and increased risk of certain cancers

  
  

  Alcohol consumption can increase estrogen levels in the blood and urine
• Progestogens: Hormones produced by the ovaries during certain phases of the menstrual cycle and in the placenta during pregnancy. They cause changes in the uterine lining and stimulate the development of mammary glands.
• Androgens: The principal androgenic steroid is testosterone, secreted primarily from the testes but also in small amounts from the adrenal glands and ovaries. It stimulates the development of male genital tract and promotes protein generation and increased muscle mass.
• Thyroid gland: Located in front of the windpipe, it produces thyroxine (T4) and triiodothyronine (T3) hormones that regulate metabolism, body temperature, and various metabolic processes. Thyroid hormone is also important for the development of the central nervous system and bone growth.
• Calcitonin: Produced by parafollicular C cells in the thyroid gland, it helps maintain normal calcium levels in the blood by reducing the release of calcium from bones and inhibiting calcium reabsorption in the kidneys.
• Parathyroid glands: Located behind the thyroid gland, they produce parathyroid hormone (PTH) which increases calcium levels in the blood by promoting calcium reabsorption from urine, release of stored calcium from bones, and bone resorption.
• 1,25-dihydroxycholecalciferol, a derivative of vitamin D, facilitates the functions of PTH
• Other hormones involved in regulating calcium levels and bone metabolism include estrogens, glucocorticoids, and growth hormone
• Hormones produced by target glands are regulated by pituitary hormones, controlled by hypothalamic hormones
• Examples of regulatory hormonal cascades include the hypothalamic-pituitary-adrenal (HPA) axis, hypothalamic-pituitary-gonadal (HPG) axis, and hypothalamic-pituitary-thyroidal (HPT) axis.
• Progesterone: A hormone that is involved in the menstrual cycle and acts on the hypothalamus and pituitary gland in a stimulatory or inhibitory manner.
• LH (Luteinizing hormone): Stimulates the testes in men to release testosterone and feeds back on the hypothalamus and pituitary.
• TSH (Thyroid-stimulating hormone): Stimulates the thyroid gland to produce thyroid hormones T3 and T4, which increase cell metabolism and feed back on the hypothalamus and pituitary.