Androgen and Mineralocorticoid Synthesis
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Questions and Answers

What is the major androgen precursor involved in androgen synthesis?

  • Progesterone
  • Androstenedione
  • Testosterone
  • Dehydroepiandrosterone (DHEA) (correct)

    • Which enzyme is involved in the conversion of 17α-hydroxyprogesterone into androstenedione?

  • Hydroxysteroid dehydrogenase
  • Cortisol synthase
  • Δ5,4 isomerase (correct)
  • Aldosterone synthase

    • Where is aldosterone primarily produced in the adrenal glands?

  • Medulla
  • Zona fasciculata
  • Zona glomerulosa (correct)
  • Zona reticularis

    • What regulates the production of adrenal androgens?

    <p>K+ levels and angiotensin II</p> Signup and view all the answers

    In testicular steroidogenesis, which cells are primarily responsible for synthesizing testicular androgens?

    <p>Leydig cells</p> Signup and view all the answers

    What is the result of the reduction of androstenedione at the C17 position?

    <p>Production of testosterone</p> Signup and view all the answers

    Which statement accurately describes the process of glucocorticoid synthesis?

    <p>C11 hydroxylation should occur last.</p> Signup and view all the answers

    Which of the following correctly represents a consequence of increased adrenal androgen production?

    <p>Impeded glucocorticoid biosynthesis</p> Signup and view all the answers

    What is the structure of epidermal growth factor (EGF) receptors similar to?

    <p>Insulin receptors</p> Signup and view all the answers

    What happens when a ligand binds to growth hormone and prolactin receptors?

    <p>It activates the JakStat pathway.</p> Signup and view all the answers

    Which is a characteristic of polypeptide and protein hormone receptors?

    <p>They alter cAMP production through G proteins.</p> Signup and view all the answers

    What is the role of the receptor domain in hormone receptors?

    <p>It recognizes and binds hormones.</p> Signup and view all the answers

    What is true about orphan receptors in the nuclear receptor superfamily?

    <p>They lack known ligands.</p> Signup and view all the answers

    How do G protein-coupled hormone receptors primarily transmit signals?

    <p>By altering the production of cAMP.</p> Signup and view all the answers

    What effect does dissociation have on hormone-receptor interaction?

    <p>It results in termination of hormone activity.</p> Signup and view all the answers

    What is a common feature of hormone receptors that span the plasma membrane?

    <p>They are involved in the coupling of hormone recognition to intracellular functions.</p> Signup and view all the answers

    What is a characteristic feature of autocrine signaling?

    <p>Hormones act on the cell that produced them.</p> Signup and view all the answers

    Which factor does NOT influence the binding affinity of a hormone to transport proteins?

    <p>Concentration of receptor on the target cell</p> Signup and view all the answers

    What primarily defines a target organ for hormone action?

    <p>The presence of receptors that bind the hormone</p> Signup and view all the answers

    What role does post-receptor desensitization play in hormone signaling?

    <p>It may result in down-regulation of receptors.</p> Signup and view all the answers

    How does the rate of hormone clearance from plasma affect hormone activity?

    <p>A slower clearance rate increases hormone activity.</p> Signup and view all the answers

    Which statement about insulin receptors is accurate?

    <p>They consist of two different protein subunits linked by disulfide bonds.</p> Signup and view all the answers

    Which of the following factors does NOT impact the state of hormone receptors on the target cell?

    <p>External temperature and environment</p> Signup and view all the answers

    What aspect of hormone action involves converting inactive forms to active forms?

    <p>Activation mechanisms</p> Signup and view all the answers

    What is the role of the malphigian layer of the epidermis in vitamin D production?

    <p>It produces 7-dehydrocholesterol from sunlight.</p> Signup and view all the answers

    Which organ is responsible for the hydroxylation at the C1 position of 25(OH)2D?

    <p>Kidney</p> Signup and view all the answers

    What type of hormones are synthesized from cholesterol?

    <p>Steroid hormones</p> Signup and view all the answers

    What is a precursor hormone for glucocorticoids?

    <p>Cholesterol</p> Signup and view all the answers

    What is the primary function of thyroid hormones?

    <p>Regulate metabolic rate</p> Signup and view all the answers

    Which of the following hormones are produced by the adrenal glands?

    <p>Glucocorticoids and mineralocorticoids</p> Signup and view all the answers

    What is a common precursor for reproductive hormones in the ovaries?

    <p>Cholesterol</p> Signup and view all the answers

    Which hormone undergoes mandatory 25 hydroxylation in the endoplasmic reticulum?

    <p>Vitamin D</p> Signup and view all the answers

    What is the rate limiting step in the hydroxylation of cholesterol?

    <p>Delivery of cholesterol to the inner mitochondrial membrane</p> Signup and view all the answers

    Which enzyme is responsible for the hydroxylation at C17 in the steroidogenesis process?

    <p>17α-hydroxylase</p> Signup and view all the answers

    Which hormone is primarily produced from the hydroxylation of pregnenolone?

    <p>Progesterone</p> Signup and view all the answers

    What condition is associated with increased aromatase activity leading to estrogen formation?

    <p>Obesity</p> Signup and view all the answers

    During pregnancy, which estrogen is predominantly formed by the placenta?

    <p>Estriol</p> Signup and view all the answers

    Which of the following hormones is classified under ovarian steroidogenesis?

    <p>17B-estradiol</p> Signup and view all the answers

    Which enzyme is NOT involved in the process of steroid hydroxylation mentioned?

    <p>Aromatase</p> Signup and view all the answers

    What is the clinical implication of using aromatase inhibitors?

    <p>Decrease estrogen formation in breast cancer treatment</p> Signup and view all the answers

    Study Notes

    Androgen and Steroid Synthesis

    • Major androgen precursor is Dehydroepiandrosterone (DHEA), produced in the adrenal cortex.
    • Aldosterone, formed from pregnenolone → progesterone through several enzymes (including aldosterone synthase), regulates blood pressure and electrolyte balance.
    • Key androgen formed is Testosterone, produced by reducing androstenedione at the C17 position.
    • Androstenedione is a more potent androgen synthesized in adrenal cortex from 17α-hydroxyprogesterone.
    • Adrenal androgen production can increase significantly when glucocorticoid biosynthesis is impaired.
    • Androgenital syndrome arises from excess androgen production.

    Glucocorticoid and Testicular Steroidogenesis

    • Glucocorticoid synthesis requires three hydroxylases located in zona fasciculata and reticularis of adrenal cortex.
    • Hydroxylation of C11 is a slow process, crucial for proper steroid hormone synthesis.
    • In testes, Leydig cells synthesize androgens such as testosterone, acting in a paracrine and autocrine manner.

    Determinants of Target Cell Response

    • Target cell response to hormones is influenced by the number and state of specific receptors present in cells.
    • Metabolism of hormones in target cells can activate or inactivate hormonal functions.
    • Factors within the cell may facilitate or hinder the hormonal response.
    • Up-regulation or down-regulation of receptors can modify cellular responsiveness.
    • Hormone clearance from the plasma affects overall activity, based on metabolic degradation or excretion.

    Receptors and Their Functions

    • Insulin receptor is a heterotetramer (α2β2) that binds insulin and activates its signaling pathway through the tyrosine protein kinase domain.
    • Insulin-like Growth Factor I (IGF-I) and Epidermal Growth Factor (EGF) receptors share structural similarities with insulin receptors but activate different signaling pathways (JakStat pathway).
    • Polypeptide hormones and catecholamine receptors alter cAMP production, involving G protein mechanisms.
    • Nuclear receptors for steroid and thyroid hormones regulate gene transcription and can be classified as orphan receptors if no ligand is known.

    Hormone Classification and Synthesis

    • Hormones are synthesized in discrete organs designed for specific hormonal functions (e.g., adrenal glands, pituitary).
    • Hormones display chemical diversity and are synthesized from varied chemical building blocks, with cholesterol providing common precursors.
    • Vitamin D is produced in skin via 7-dehydrocholesterol under UV light, undergoing hydroxylation to become biologically active.
    • Aromatase activity is crucial for converting androgens into estrogens, impacting various health conditions.

    Clinical Implications and Hormonal Disorders

    • Aromatase inhibitors can inhibit estrogen formation, serving as treatment for breast cancer in post-menopausal women.
    • Increased aromatase activity linked to conditions like obesity can lead to heightened estrogen levels, termed "Estrogenization."
    • Hormonal imbalances can be influenced by age, obesity, and liver diseases, necessitating comprehensive hormonal assessments and targeted treatments.

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    Description

    Explore the synthesis pathways of androgens and mineralocorticoids in this quiz. Focus on key precursors like Dehydroepiandrosterone (DHEA) and hormones such as aldosterone. Test your knowledge of the adrenal cortex and its functions in hormone production.

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