Endocrinology Practice Questions

Q: Insulin decreases:

Lipolysis. **Explanation:** Insulin is the body’s primary **anabolic hormone**, secreted by the beta cells of the Islets of Langerhans. Its fundamental role is to promote energy storage and inhibit the breakdown of stored fuels (catabolism). **Why Lipolysis is the correct answer:** Insulin is a potent **anti-lipolytic** hormone. It inhibits the enzyme **Hormone-Sensitive Lipase (HSL)** in adipose tissue. HSL is responsible for breaking down stored triglycerides into free fatty acids and glycerol. By inhibiting HSL, insulin decreases the concentration of circulating free fatty acids, thereby promoting fat storage and preventing ketogenesis. **Analysis of Incorrect Options:** * **A. Glucose uptake:** Insulin **increases** glucose uptake in peripheral tissues (skeletal muscle and adipose tissue) by inducing the translocation of **GLUT-4** transporters to the cell membrane. * **B. Glycogen synthesis:** Insulin **increases** glycogenesis by activating the enzyme **Glycogen Synthase**, ensuring excess glucose is stored in the liver and muscles. * **C. Protein synthesis:** Insulin is anabolic for proteins; it **increases** amino acid uptake and protein synthesis while inhibiting proteolysis. **NEET-PG High-Yield Pearls:** * **GLUT-4** is the only insulin-dependent glucose transporter (found in heart, skeletal muscle, and adipose tissue). * Insulin stimulates **Lipoprotein Lipase (LPL)** in capillary walls to clear chylomicrons from the blood, but inhibits **Hormone-Sensitive Lipase (HSL)** inside adipocytes. * **Key Enzyme Regulation:** Insulin activates Phosphofructokinase (Glycolysis) and Glycogen Synthase (Glycogenesis), while inhibiting Fructose-1,6-bisphosphatase (Gluconeogenesis).

Q: What is the half-life of T3?

2 days. The half-life of thyroid hormones is primarily determined by their affinity for plasma proteins, specifically **Thyroxine-Binding Globulin (TBG)**. ### **Explanation of the Correct Answer** **Option B (2 days)** is correct. Triiodothyronine (T3) has a significantly lower affinity for TBG compared to T4. Because less T3 is protein-bound (~99.7%) and more exists in the free, metabolically active form, it is cleared from the circulation much faster. Its half-life is approximately **1 to 2 days** (24–48 hours). ### **Analysis of Incorrect Options** * **Option A (10 hours):** This is too short for thyroid hormones. While T3 is "fast-acting," its protein binding still allows it to persist longer than catecholamines or peptide hormones. * **Option C (6 days):** This is the approximate half-life of **Thyroxine (T4)**. T4 is >99.9% protein-bound and has a much higher affinity for TBG, which acts as a reservoir, slowing its clearance. * **Option D (10 days):** This exceeds the physiological half-life of any thyroid hormone. ### **NEET-PG High-Yield Pearls** * **Potency vs. Half-life:** T3 is **4 times more potent** than T4 but has a shorter half-life. * **The "Pro-hormone":** T4 is considered a pro-hormone; most T3 in the body (80%) is produced by the peripheral deiodination of T4 by the enzyme **5'-deiodinase**. * **Reverse T3 (rT3):** Formed by the action of 5-deiodinase; it is metabolically inactive. * **Clinical Correlation:** Due to the long half-life of T4 (6–7 days), it takes about 4–6 weeks to reach a new steady state after initiating Levothyroxine therapy. This is why TSH is not rechecked sooner than 6 weeks.

Q: All of the following are known effects of corticosteroids on the skin and connective tissue except?

Hyperpigmentation. **Explanation:** The correct answer is **Hyperpigmentation**. Corticosteroids actually cause **hypopigmentation** (skin lightening) by inhibiting the activity of melanocytes and reducing the production of melanocyte-stimulating hormone (MSH). Hyperpigmentation is typically seen in conditions of corticosteroid *deficiency* (like Addison’s disease) due to the compensatory increase in ACTH, which shares a precursor with MSH. **Analysis of Options:** * **A & B (Antiproliferative effects):** Glucocorticoids inhibit the mitotic activity of both **keratinocytes** (epidermis) and **fibroblasts** (dermis). This is the pharmacological basis for using topical steroids in hyperproliferative skin disorders like psoriasis. * **C (Loss of collagen):** By inhibiting fibroblasts, steroids decrease the synthesis of Type I and III collagen and glycosaminoglycans. This leads to the hallmark clinical features of steroid excess: skin thinning (atrophy), easy bruising, and the formation of wide, purple **striae**. **High-Yield Clinical Pearls for NEET-PG:** * **Iatrogenic Cushing Syndrome:** Prolonged steroid use leads to a "moon face," "buffalo hump," and truncal obesity, but the skin remains thin and fragile. * **Wound Healing:** Corticosteroids **delay wound healing** because they inhibit the inflammatory phase and reduce the fibroblastic repair required for wound contraction. * **Topical Potency:** Fluorinated steroids are more potent but carry a higher risk of causing irreversible skin atrophy and telangiectasia.

Q: What is the recommended daily intake of Vitamin A for adults?

4000 IU. **Explanation:** The recommended dietary allowance (RDA) for Vitamin A is essential for maintaining normal vision, epithelial integrity, and immune function. According to the **ICMR (Indian Council of Medical Research)** and standard physiological guidelines, the daily requirement for a healthy adult is approximately **600–1000 µg of Retinol**, which translates to roughly **2000–4000 International Units (IU)** depending on the specific population group (gender and activity level). In the context of standard medical examinations, **4000 IU** is considered the upper threshold of the normal daily requirement for adults to maintain adequate hepatic stores. **Analysis of Options:** * **A & B (1000–2000 IU):** These values are generally considered inadequate for adults. 1000 IU is closer to the requirement for infants, while 2000 IU may be the bare minimum to prevent deficiency but does not meet the optimal RDA for an active adult. * **C (3000 IU):** While closer to the requirement for adult females, it is often superseded by the 4000 IU recommendation in competitive exams to cover the broader adult population (including males). * **D (4000 IU):** This is the standard high-yield value for adult RDA, ensuring sufficient Retinol Binding Protein (RBP) saturation. **Clinical Pearls for NEET-PG:** * **Storage:** Vitamin A is stored in the **Ito cells (Stellate cells)** of the liver. * **Earliest Sign of Deficiency:** Conjunctival xerosis (though **Night Blindness/Nyctalopia** is the earliest *symptom*). * **Bitot’s Spots:** Triangular, pearly-white foamy patches on the bulbar conjunctiva (pathognomonic for deficiency). * **Toxicity:** Chronic ingestion of >25,000 IU/day can lead to **Pseudotumor Cerebri** (idiopathic intracranial hypertension) and hepatotoxicity.

Q: Inhibition of prolactin is caused by:

Dopamine. **Explanation:** The secretion of Prolactin from the anterior pituitary is unique because it is under **tonic inhibitory control** by the hypothalamus. **A. Dopamine (Correct):** Dopamine is the primary **Prolactin-Inhibiting Factor (PIF)**. It is secreted by the tuberoinfundibular dopaminergic (TIDA) neurons of the hypothalamus into the hypophyseal portal system. It binds to **D2 receptors** on the lactotrophs in the anterior pituitary, inhibiting the synthesis and release of prolactin [1]. **B. Dobutamine:** This is a synthetic catecholamine that acts primarily as a $\beta_1$-adrenergic agonist used in cardiac failure. It does not play a physiological role in pituitary hormone regulation. **C. TRH (Thyrotropin-Releasing Hormone):** TRH is a potent **stimulator** of prolactin release [1]. In patients with primary hypothyroidism (where TRH levels are elevated), hyperprolactinemia is a common clinical finding [2]. **D. AT-II (Angiotensin II):** While AT-II has various systemic effects on blood pressure and aldosterone, it is generally considered a weak stimulator of prolactin release in certain physiological contexts, not an inhibitor. **High-Yield Clinical Pearls for NEET-PG:** * **The "Stalk Effect":** Any compression of the pituitary stalk (e.g., by a craniopharyngioma) prevents dopamine from reaching the pituitary, leading to **increased** prolactin levels (disinhibition) [2]. * **Drug-Induced Hyperprolactinemia:** Antipsychotics (D2 antagonists like Haloperidol or Risperidone) and Metoclopramide block dopamine's inhibitory effect, leading to galactorrhea and amenorrhea [2]. * **Prolactinoma Treatment:** Dopamine agonists (Cabergoline, Bromocriptine) are the first-line treatment to shrink the tumor and normalize prolactin levels [3].

Q: ACTH levels are increased in all of the following conditions except:

Evening. The regulation of Adrenocorticotropic Hormone (ACTH) is governed by the hypothalamic-pituitary-adrenal (HPA) axis and is highly sensitive to stress and circadian rhythms. **Explanation of the Correct Answer:** **C. Evening:** ACTH secretion follows a distinct **diurnal (circadian) rhythm**. Levels are highest in the early morning (around 6:00 AM to 8:00 AM) and gradually decline throughout the day, reaching their **nadir (lowest point) in the evening** and early hours of sleep (around midnight). Therefore, ACTH levels are decreased, not increased, in the evening compared to morning levels. **Explanation of Incorrect Options:** * **A. Exercise:** Physical exertion is a potent physiological stressor that activates the HPA axis, leading to a significant increase in CRH and subsequent ACTH release to mobilize energy stores. * **B. Emotions:** Psychological stress (anxiety, fear, or emotional trauma) triggers the amygdala to stimulate the hypothalamus, resulting in elevated ACTH levels. * **C. Tumors:** Pathological increases occur in **Cushing’s Disease** (pituitary adenoma secreting ACTH) or **Ectopic ACTH Syndrome** (e.g., Small Cell Carcinoma of the lung). **High-Yield Clinical Pearls for NEET-PG:** * **Diurnal Variation:** To diagnose Cushing’s syndrome, the loss of this diurnal rhythm (elevated late-night cortisol/ACTH) is a key diagnostic finding. * **Primary vs. Secondary:** ACTH is **increased** in Addison’s disease (Primary Adrenal Insufficiency) due to loss of negative feedback, but **decreased** in Secondary Adrenal Insufficiency (Pituitary failure). * **Nelson’s Syndrome:** Rapid increase in ACTH levels and skin hyperpigmentation following bilateral adrenalectomy due to the growth of a pre-existing pituitary adenoma.

Q: Which of the following hormones exhibits genomic action?

All of these. ### Explanation The correct answer is **D. All of these**. **1. Underlying Medical Concept: Mechanism of Hormone Action** Hormones are generally classified into two groups based on their solubility and receptor location. **Genomic action** refers to the process where a hormone binds to an intracellular receptor (either in the cytoplasm or nucleus), acts as a ligand-activated transcription factor, and directly influences gene expression (mRNA synthesis). Lipid-soluble hormones can easily cross the cell membrane to exert these effects. These include: * **Steroid Hormones:** Cortisol, Aldosterone, Estrogen, Progesterone, Testosterone. * **Thyroid Hormones:** $T_3$ and $T_4$. * **Vitamin D:** 1,25-dihydroxycholecalciferol (Calcitriol). * **Retinoids:** Vitamin A. **2. Analysis of Options** * **Thyroid Hormone (A):** Binds to receptors already attached to DNA in the nucleus (TR-RXR complex). It is a classic example of genomic action. * **1,25-dihydroxycholecalciferol (B):** As a steroid-like hormone, it binds to the Vitamin D Receptor (VDR) in the nucleus to regulate calcium-binding protein synthesis. * **Cortisol (C):** A glucocorticoid that binds to cytoplasmic receptors, translocates to the nucleus, and binds to Glucocorticoid Response Elements (GRE) on DNA. **3. High-Yield Clinical Pearls for NEET-PG** * **Speed of Action:** Genomic actions are **slow** (minutes to hours) because they require protein synthesis. In contrast, peptide hormones (like Insulin or Epinephrine) use second messengers (cAMP, $IP_3/DAG$) for **fast** non-genomic actions. * **Exception:** Thyroid hormones are amino-acid derivatives but behave like steroids (intracellular receptors). * **Receptor Location:** * **Cytoplasmic:** Glucocorticoids, Mineralocorticoids. * **Nuclear:** Thyroid hormones, Retinoic acid, Estrogen, Vitamin D.

Q: Corticosteroids suppress:

Adrenocorticotropic Hormone (ACTH). ### Explanation **1. Why Option B is Correct:** The regulation of the adrenal cortex occurs via the **Hypothalamic-Pituitary-Adrenal (HPA) axis**. Corticosteroids (specifically glucocorticoids like cortisol) exert a powerful **negative feedback** effect. When systemic levels of corticosteroids rise, they act on: * **The Anterior Pituitary:** To directly inhibit the secretion of **ACTH**. * **The Hypothalamus:** To inhibit the release of Corticotropin-Releasing Hormone (CRH). This feedback loop ensures hormonal homeostasis. Clinically, exogenous steroid administration mimics this effect, leading to the suppression of endogenous ACTH. **2. Why Other Options are Incorrect:** * **Option A (GH):** While chronic, high-dose glucocorticoids can interfere with growth in children by inhibiting IGF-1 and affecting growth plates, they are not the primary physiological suppressors of GH. GH is primarily regulated by GHRH and Somatostatin. * **Options C & D (FSH & LH):** These gonadotropins are regulated by the Hypothalamic-Pituitary-Gonadal (HPG) axis via GnRH. While extreme stress (high cortisol) can indirectly disrupt the menstrual cycle, corticosteroids do not directly suppress FSH and LH as their primary mechanism of action. **3. High-Yield Clinical Pearls for NEET-PG:** * **Adrenal Atrophy:** Prolonged exogenous steroid use leads to chronic ACTH suppression. Without ACTH (the trophic hormone), the adrenal cortex undergoes **disuse atrophy**. * **Steroid Tapering:** This is why steroids must be tapered slowly; sudden withdrawal can lead to **Acute Adrenal Insufficiency** because the atrophied adrenals cannot immediately resume cortisol production. * **Cushing’s Disease vs. Syndrome:** In Cushing’s *Disease* (pituitary adenoma), ACTH is high. In Cushing’s *Syndrome* due to an adrenal tumor, ACTH is suppressed due to the negative feedback of excess cortisol.

Question 1

Insulin decreases:

Accepted Answer

Lipolysis

Answer

Glucose uptake

Answer

Glycogen synthesis

Answer

Protein synthesis

Question 2

What is the half-life of T3?

Accepted Answer

2 days

Answer

10 hours

Answer

6 days

Answer

10 days

Question 3

All of the following are known effects of corticosteroids on the skin and connective tissue except?

Accepted Answer

Hyperpigmentation

Answer

Antiproliferative effect on fibroblasts

Answer

Antiproliferative effect on keratinocytes

Answer

Loss of collagen

Question 4

What is the recommended daily intake of Vitamin A for adults?

Accepted Answer

4000 IU

Answer

1000 IU

Answer

2000 IU

Answer

3000 IU

Question 5

Inhibition of prolactin is caused by:

Accepted Answer

Dopamine

Answer

Dobutamine

Answer

TRH

Answer

AT-II

Question 6

Axillary hair growth is stimulated by which hormone?

Accepted Answer

Testosterone

Answer

Estrogen

Answer

Prolactin

Answer

Androgens

Question 7

ACTH levels are increased in all of the following conditions except:

Accepted Answer

Evening

Answer

Exercise

Answer

Emotions

Answer

Tumors

Question 8

Which of the following hormones exhibits genomic action?

Accepted Answer

All of these

Answer

Thyroid hormone

Answer

1,25-dihydroxycholecalciferol

Answer

Cortisol

Question 9

Chvostek’s sign is elicited by:

Accepted Answer

Stimulating the facial nerve by tapping over the parotid gland

Answer

Inflating a blood pressure cuff in the arm for 5 minutes

Answer

Tapping over the extensor pollicis brevis tendon

Answer

Tapping over the flexor retinaculum

Question 10

Corticosteroids suppress:

Accepted Answer

Adrenocorticotropic Hormone (ACTH)

Answer

Growth Hormone (GH)

Answer

Follicle-Stimulating Hormone (FSH)

Answer

Luteinizing Hormone (LH)

Endocrinology — MCQs

Endocrinology — MCQs

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