Lipid-soluble hormone

(noun)

A lipophilic hormone that passes through the plasma membrane of a cell, binds to an intracellular receptor, and changes gene expression.

Related Terms

  • Water-soluble hormone
  • hormone

Examples of Lipid-soluble hormone in the following topics:

  • Mechanisms of Hormone Action

    • Hormones activate target cells by diffusing through the plasma membrane of the target cells (lipid-soluble hormones) to bind a receptor protein within the cytoplasm of the cell, or by binding a specific receptor protein in the cell membrane of the target cell (water-soluble proteins).
    • Lipid: Steroid hormones that contain lipids synthesized from cholesterol and eicosanoids that contain lipids synthesized from the fatty acid chains of phospholipids found in the plasma membrane.
    • Nuclear hormone receptors are activated by a lipid-soluble hormone such as estrogen, binding to them inside the cell.
    • Lipid-soluble hormones can cross the plasma membrane.
    • Water-soluble hormones, such as epinephrine, bind to a cell-surface localized receptor, initiating a signaling cascade using intracellular second messengers.
  • Hormone Receptors

    • A hormone receptor is a molecule that binds to a specific hormone.
    • Receptors for peptide hormones tend to be found on the plasma membrane of cells, whereas receptors for lipid-soluble hormones are usually found within the cytoplasm.
    • The hormone activity within a target cell is dependent on the effective concentration of hormone-receptor complexes that are formed.
    • Many hormones are composed of polypeptides—such as thyroid-stimulating hormones, follicle-stimulating hormones, luteinizing hormones, and insulin.
    • These molecules are not lipid-soluble and therefore cannot diffuse through cell membranes.
  • Direct Gene Activation and the Second-Messenger System

    • Hormones can alter cell activity by binding with a receptor.
    • Upon binding to a hormone the receptor and hormone translocate into the nucleus, and bind to specific sequences of DNA known as hormone response elements (HREs).
    • Most hormone receptors are G protein-coupled receptors.
    • Hormone binding to the NR triggers translocation to the nucleus, where the NR binds to a specific sequence of DNA known as a hormone response element (HRE).
    • Distinguish between the hormone mechanisms of direct gene activation and the second-messenger system
  • Chemistry of Hormones

    • There are three classes of hormones: peptide hormones, lipid hormones, and monoamine hormones.
    • Some peptide hormones contain carbohydrate side chains  and are termed glyco-proteins, such as the follicle-stimulating hormone.
    • Lipid and phospholipid-derived hormones are produced from lipids such as linoleic acid and arachidonic acid.
    • Steroid hormones, which form the majority of lipid hormones, are derived from carbohydrates; for example, testosterone is produced primarily in the testes and plays a key role in development of the male reproductive system.
    • Eicosanoids are also lipid hormones that are derived from fatty acids in the plasma membrane.
  • Absorption of Monosaccharides, Amino Acids, Dipeptides, Tripeptides, Lipids, Electrolytes, Vitamins, and Water

    • The three major classes of nutrients that undergo digestion are proteins, lipids (fats), and carbohydrates.
    • Lipids (fats) are degraded into fatty acids and glycerol.
    • The fat soluble vitamins A, D, and E are absorbed in the upper small intestine.
    • Of the water soluble vitamins, transport of Folate and B12 across the apical membrane are Na+ independent, but the other water soluble vitamins are absorbed by Na+ co-transporters.
    • In humans, electrolyte homeostasis is regulated by hormones such as antidiuretic, aldosterone, and parathyroid hormone.
  • Digestive Processes of the Small Intestine

    • The small intestine uses different enzymes and processes to digest proteins, lipids, and carbohydrates.
    • These enzymes enter the small intestine in response to the hormone cholecystokinin, which is produced in response to the presence of nutrients.
    • The hormone secretin also causes bicarbonate to be released into the small intestine from the pancreas, neutralizing the potentially harmful acid coming from the stomach.
    • The three major classes of nutrients that undergo digestion are proteins, lipids (fats), and carbohydrates.
    • Lipids (fats) are degraded into fatty acids and glycerol.
  • Regulation of Blood Cholesterol Levels

    • Cholesterol is only slightly soluble in water; it can dissolve and travel in the water-based bloodstream at exceedingly small concentrations.
    • Since cholesterol is insoluble in blood, it is transported in the circulatory system within lipoproteins , which are complex discoidal particles that have an exterior composed of amphiphilic proteins and lipids whose outward-facing surfaces are water-soluble and inward-facing surfaces are lipid-soluble; triglycerides and cholesterol esters are carried internally.
    • In addition to providing a soluble means for transporting cholesterol through the blood, lipoproteins have cell-targeting signals that direct the lipids they carry to certain tissues.
    • The more lipid and less protein a lipoprotein has, the less dense it is.
    • Also, HDL particles are thought to transport cholesterol back to the liver for excretion or to other tissues that use cholesterol to synthesize hormones in a process known as reverse cholesterol transport (RCT).
  • The Anterior Pituitary

    • Thyroid-stimulating hormone is a glycoprotein hormone that affects the thyroid gland and the secretion of thyroid hormones.
    • Follicle-stimulating hormone is a glycoprotein hormone that targets the gonads and effects the growth of the reproductive system.
    • Luteinizing hormone is a glycoprotein hormone that targets the gonads to effect sex-hormone production.
    • Growth hormone is a polypeptide hormone that targets the liver and adipose tissue and promotes growth through lipid and carbohydrate metabolism.
    • Hormone secretion from the anterior pituitary gland is regulated by hormones secreted by the hypothalamus.
  • Blood Plasma

    • It is an aqueous solution containing about 90% water, 8% soluble blood plasma proteins, 1% electrolytes, and 1% elements in transit.
    • Hormones and nutrients such as glucose, amino acids and proteins, lipids and fatty acids, and vitamins are also dissolved in the plasma.
  • Calcium and Phosphate Balance Regulation

    • The solubility product of Ca and P is close to saturation in plasma.
    • Even if it was all soluble it is not all absorbed as it combines with phosphates in the intestinal secretions.
    • Absorption is controlled by vitamin D while excretion is controlled by parathyroid hormones.
    • This hormone also causes phosphate to leach out of bone.
    • Plasma phosphate has no direct effect on parathyroid hormone secretion; however, if it is elevated it combines with Ca++, decreasing ionized Ca++ in plasma, and thereby increasing parathyroid hormone secretion.
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