Endocrinology Chapter 5 Quiz

Hormone Definition

• Hormones are regulatory substances produced in an organism and transported in tissue fluids (like blood) to stimulate specific cells or tissues.
• They are produced by one tissue and carried by the bloodstream to another tissue to influence physiological activity, such as growth or metabolism.

Hormone Biochemistry

• Hormones are composed of different biochemical components.
• Some hormones are peptides or proteins, hydrophilic molecules with relatively large molecular weight, and synthesized through mRNA-directed processes. They are stored in membrane-bound vesicles and cannot readily diffuse across cell membranes. They interact with receptors in cell membranes.
• Other hormones are steroid or fatty acid derivatives, hydrophobic molecules with relatively small molecular weight. They are synthesized through multi-step enzyme-mediated processes and are not stored in signaling cells. They readily cross cell membranes and interact with intracellular or membrane receptors.

Peptide Hormone Production

• Peptide hormones are produced through translation and transcription from a gene, or from other proteins.

Up/Downregulation of Peptide Hormone Production

• Peptide hormone production can be upregulated (increased) or downregulated (decreased).

Hormone Processing

• Hormones (especially peptides) are processed within an endocrine cell. This involves several steps: synthesis, prohormone packaging, prohormone processing, hormone storage, and hormone secretion.

Ghrelin and Obestatin

• Ghrelin is a peptide hormone involved in stimulating appetite.
• Obestatin is another peptide hormone associated with decreasing appetite.

Steroid and Fatty Acid Derivatives

• Steroid and fatty acid derivatives are produced through several steps, often multi-step processes.
• Examples of these derivatives include: prostaglandins, thromboxanes, leukotrienes, progesterone, estradiol, and testosterone. Fatty acid derivatives include arachidonic acid.

Cholesterol Metabolism and Steroid Production

• The first step in steroid synthesis involves the conversion of cholesterol to pregnenolone.
• This conversion occurs in the inner mitochondrial membrane.
• The rate-limiting step is the transport of cholesterol from the cytoplasm to the mitochondria. This is carried out by the Steroidogenic Acute Regulatory Protein (StAR).

Steroid Synthesis

• The synthesis of steroids involves multiple steps and enzymes as depicted in the diagrams.

Enzyme Names and "Old" Names

• There are specific enzymes involved in the synthesis of steroid hormones. These enzymes have names, as well as older names that may be used in some contexts.

Steroidogenic Enzymes

• Some key enzymes involved in steroid hormone synthesis (Aromatase, 450scc) and their related names are provided.

Biochemistry of Hormones - Questions and Answers

• The presentation asks several questions about the relationship between hormone concentration/production and secretion, with the suggested answer of "yes" for most of them.

Hormone Measurements - General Methods

• Three methods are used for measuring hormones: biological, immunological, and chemical.
• Biological methods involve measuring how the hormone affects a target organ or tissue.
• Immunological and chemical methods, including chromatography and mass spectrometry, measure aspects of the hormone's chemical structure or composition.

Biological Assay Examples

• Several hormones, and assay systems to test them, have been provided, along with methods used to evaluate them.

Immunoassay Principles and Ingredients

• Immunoassays measure hormones via specialized chemical reactions that utilize antibodies and labeled hormones.
• Key factors to consider in immunoassays are the specificity of the antibodies and the sensitivity.
• The method uses the principle that the quantity of a hormone can be identified by measuring the endpoint signaling.

Competitive Binding Assay

Examples, diagrams, and detailed explanation of competitive binding assay are included. This method includes standards to relate to the samples.

Antigen Capture Assay

• This assay involves a similar approach to measures the levels of hormones.

Validation of an Assay

• Assay validation involves three steps: parallelism, recovery, and cross-reactivity. Parallelism assesses whether dilutions of the sample will produce a similar response to dilutions of the standard. Recovery measures the correct detection of the target hormone in the presence of a known standard. Cross-reactivity evaluates whether there is any overlap or other hormones/factors that can interact with the test.

Common Problems with Immunoassays

• Factors to consider when using immunoassay methods include the sensitivity and specificity of hormone detection as well as the challenges of the lack of antibodies that recognize certain hormones.

Chemical Methods

• These methods for measuring hormones are used when biological or immunological methods are not available, evaluating unique aspects of hormones such as their chemical composition. These methods usually use specialized chemicals, such as chromatography and mass spectrometry.

Test your knowledge on the types and synthesis of hormones, specifically focusing on peptide and steroid hormones. This quiz covers their biochemical composition, production processes, and key enzymes involved in their synthesis. Dive into the specifics of hormonal regulation and precursor molecules in this challenging quiz.