Steroid and Sex Hormones | Essay Questions | Ompath Study

Practice 9 structured short- and long-answer medical questions on Steroid and Sex Hormones. Review model answers for exam revision.

Essay Questions and Answers

1. Q1. ### Overview of Steroid and Sex Hormones

   Answer: Steroid hormones are lipophilic molecules derived from cholesterol. They are categorized into several functional groups: * **Glucocorticoids**: e.g., Cortisol (stress response and metabolism). * **Mineralocorticoids**: e.g., Aldosterone (electrolyte balance and blood pressure). * **Androgens**: e.g., Testosterone (male reproductive development and secondary characteristics). * **Estrogens**: e.g., Estradiol and Estrone (female reproductive cycle and pregnancy). * **Progestogens**: e.g., Progesterone (menstrual cycle regulation and pregnancy maintenance). ### Structure and Classification Steroid hormones possess a core cyclopentanoperhydrophenanthrene ring. They are classified by the number of carbon atoms: * **C-21**: Pregnenolone, Progesterone, Aldosterone, Cortisol. * **C-19**: Testosterone, Dehydroepiandrosterone (DHEA). * **C-18**: Estradiol. * **Secosteroid**: Calcitriol (1,25-Dihydroxyvitamin D3). ### Characteristics of Steroid Hormones

2. Q2. **Lipophilic**: Derived from cholesterol; easily cross cellular membranes.

   Answer: Model answer pending

3. Q3. **Synthesis on Demand**: Not stored in vesicles; released immediately upon synthesis.

   Answer: Model answer pending

4. Q4. **Intracellular Receptors**: Bind to receptors in the cytoplasm or nucleus.

   Answer: Model answer pending

5. Q5. **Genomic Action**: Hormone-receptor complexes act as transcription factors to initiate protein synthesis.

   Answer: Model answer pending

6. Q6. **Pharmacokinetics**: Slow-acting with a long half-life compared to peptide hormones.

   Answer: ### Steroidogenesis (Synthesis) Unlike peptide hormones, steroids are not genetically encoded but are synthesized via enzymatic modification of cholesterol. #### Sources of Cholesterol * **De Novo Synthesis**: From Acetyl-CoA via the HMG-CoA reductase pathway (rate-limiting enzyme). * **Exogenous**: Uptake of Low-Density Lipoproteins (LDL) via LDL receptors. #### Initial Steps

7. Q7. **Transport**: Free cholesterol is moved from the cytoplasm to the inner mitochondrial membrane by the **Steroidogenic Acute Regulatory Protein (StAR)**. This is the rate-limiting step.

   Answer: Model answer pending

8. Q8. **Conversion**: The enzyme **Cytochrome P450scc** (side-chain cleavage) converts cholesterol to **Pregnenolone**.

   Answer: Model answer pending

9. Q9. **Regulation**: Luteinizing Hormone (LH) stimulates this process via the cAMP/PKA pathway.

   Answer: ### Transport and Metabolism * **Transport**: Steroids are hydrophobic and require carrier proteins: * **Corticosteroid-Binding Globulin (CBG)** for cortisol. * **Sex Hormone-Binding Globulin (SHBG)** for testosterone and estradiol. * **Catabolism**: Inactivated in the liver via conjugation (glucuronides or sulfates) to increase water solubility for excretion in urine (70%) and feces (20%). ### Clinical Correlations and Pathophysiology * **Aromatase Deficiency**: Results in low estrogen and high testosterone, leading to virilization in females. * **Hypogonadism**: Defined by low testosterone (Total <8 nmol/L). SHBG levels typically increase with age, further reducing bioavailable free testosterone. * **Adrenal Cortex Zones**: * *Zona Glomerulosa*: Mineralocorticoids (lacks P450c17). * *Zona Fasciculata*: Glucocorticoids. * *Zona Reticularis*: Androgens. * **Two-Cell Theory of Estrogen**: Androgens produced in theca cells are converted to estradiol by aromatase in granulosa cells under FSH influence. * **Vitamin D3**: Synthesized from 7-dehydrocholesterol in the skin via UV light, then hydroxylated in the liver and kidneys to active 1,25-(OH)2D3. * **Disorders of Sex Development (DSDs)**: Includes 5-alpha reductase deficiency, Androgen Insensitivity Syndrome, and 21-hydroxylase deficiency (Congenital Adrenal Hyperplasia).