Endocrinology Practice Questions

Q: Which of the following hormonal concentrations decreases with age?

Growth hormone. **Explanation:** The correct answer is **Growth Hormone (GH)**. This phenomenon is known as **somatopause**. GH secretion peaks during puberty and undergoes a progressive decline starting in the third decade of life (approximately 14% decrease per decade). This decline is primarily due to decreased hypothalamic GHRH secretion and increased somatostatin tone, contributing to age-related changes like decreased muscle mass (sarcopenia) and increased visceral fat. **Analysis of Options:** * **A. Parathormone (PTH):** PTH levels typically **increase** with age. This is often a secondary response to declining Vitamin D levels, reduced calcium absorption in the gut, and declining renal function in the elderly. * **B. FSH (Follicle-Stimulating Hormone):** FSH levels **increase** significantly with age, particularly in females during menopause. As ovarian follicles deplete, the loss of negative feedback from estrogen and inhibin leads to a compensatory rise in FSH and LH. * **D. Norepinephrine:** Plasma levels of norepinephrine generally **increase** with age due to increased sympathetic nervous system activity and reduced clearance from the synaptic cleft. **High-Yield NEET-PG Pearls:** * **Hormones that Decrease with Age:** Growth Hormone, Melatonin, DHEA (Dehydroepiandrosterone), Testosterone, and Estrogen. * **Hormones that Increase with Age:** PTH, FSH, LH, Norepinephrine, and Vasopressin (ADH). * **Hormones that remain relatively Constant:** Thyroid hormones (T3/T4) and Cortisol (though the circadian rhythm of cortisol may flatten). * **Somatopause Clinical Correlation:** The decline in GH/IGF-1 axis is a major contributor to the "frailty syndrome" in the elderly.

Q: Where are the receptors for parathyroid hormone located?

Osteoblasts. ### Explanation **1. Why Osteoblasts are the Correct Answer:** The primary target of Parathyroid Hormone (PTH) in the bone is the **osteoblast**. Although PTH’s ultimate physiological effect is to increase bone resorption (releasing calcium into the blood), it does not act directly on osteoclasts. Instead, PTH binds to **PTH-1 receptors (GPCRs)** on osteoblasts. This binding stimulates the expression of **RANKL** (Receptor Activator of Nuclear Factor kappa-B Ligand) and decreases the secretion of Osteoprotegerin (OPG). The RANKL then binds to RANK receptors on pre-osteoclasts, triggering their maturation into active osteoclasts. Thus, osteoblasts mediate the PTH-induced activation of osteoclasts. **2. Why the Other Options are Incorrect:** * **B. Osteoclasts:** These cells lack PTH receptors. They are stimulated indirectly via the RANK/RANKL pathway initiated by osteoblasts. * **C. Periosteum:** While the periosteum contains osteoprogenitor cells, it is not the primary functional site for PTH-mediated calcium homeostasis. * **D. Cartilage:** PTH-related protein (PTHrP) acts on chondrocytes during endochondral ossification, but the systemic regulation of calcium by PTH specifically targets bone-forming cells (osteoblasts) and the kidneys. **3. NEET-PG Clinical Pearls & High-Yield Facts:** * **Dual Action:** While continuous high levels of PTH cause bone resorption, **intermittent low doses** of PTH (e.g., Teriparatide) actually stimulate osteoblastic activity and bone formation, making it a treatment for osteoporosis. * **Renal Action:** In the kidneys, PTH increases calcium reabsorption in the **Distal Convoluted Tubule (DCT)** and inhibits phosphate reabsorption in the **Proximal Convoluted Tubule (PCT)** (causing phosphaturia). * **Vitamin D:** PTH stimulates the enzyme **1-alpha-hydroxylase** in the kidneys, converting inactive Vitamin D to its active form, Calcitriol.

Q: Which of the following is NOT an endocrine function associated with the kidney?

Natriuretic peptide secretion. The kidney is a vital endocrine organ, but it is not the primary source of natriuretic peptides. ### **Why Option B is Correct** **Natriuretic peptides** (specifically ANP and BNP) are primarily secreted by the **heart**. Atrial Natriuretic Peptide (ANP) is secreted by the atrial myocytes, and Brain Natriuretic Peptide (BNP) is secreted by ventricular myocytes in response to stretch (volume overload). While the kidney is the *target* organ for these peptides (where they promote sodium excretion), it does not secrete them. ### **Why Other Options are Incorrect** * **A. Erythropoietin (EPO):** Approximately 90% of EPO is synthesized by the **peritubular interstitial cells** of the renal cortex in response to hypoxia. It stimulates RBC production in the bone marrow. * **C. 1,25-dihydroxycholecalciferol (Calcitriol):** The kidney performs the final, rate-limiting step of Vitamin D activation. The enzyme **1-alpha-hydroxylase** (located in the proximal convoluted tubule) converts 25-hydroxyvitamin D into the active form, Calcitriol. * **D. Renin:** Renin is secreted by the **Juxtaglomerular (JG) cells** of the afferent arteriole. It is the initiating enzyme of the Renin-Angiotensin-Aldosterone System (RAAS), crucial for blood pressure regulation. ### **High-Yield NEET-PG Pearls** * **Urodilatin:** A rare natriuretic peptide that *is* produced by the distal tubule, but "Natriuretic Peptide" as a general term refers to the cardiac hormones ANP/BNP. * **Chronic Kidney Disease (CKD):** Patients develop anemia primarily due to **EPO deficiency** and secondary hyperparathyroidism due to **Calcitriol deficiency**. * **Prostaglandins:** The kidney also produces PGE2 and PGI2, which act as local vasodilators to maintain renal blood flow.

Q: Sex hormone-binding globulin (SHBG) levels are decreased in which of the following conditions?

Increased androgen levels. **Explanation:** Sex hormone-binding globulin (SHBG) is a glycoprotein produced primarily by the **liver**. It binds to sex steroids (testosterone, DHT, and estradiol) to regulate their bioavailability; only the "free" hormone is biologically active. **Why Option B is Correct:** The synthesis of SHBG in the liver is inhibited by **androgens, insulin, and obesity**. Therefore, in conditions with increased androgen levels (such as PCOS or androgen-secreting tumors), SHBG levels decrease. This creates a clinical "vicious cycle": lower SHBG leads to higher levels of free (active) testosterone, further worsening androgenic symptoms like hirsutism. **Why Other Options are Incorrect:** * **A. Hyperthyroidism:** Thyroid hormones (T3/T4) **stimulate** the hepatic production of SHBG. Thus, SHBG levels are elevated in hyperthyroidism. * **C. Increased Estrogen levels:** Estrogen is a potent stimulator of SHBG synthesis. High estrogen levels increase SHBG, which is why women generally have higher levels than men. * **D. Pregnancy:** This is a state of high endogenous estrogen production, which significantly **increases** SHBG levels (often 5–10 fold). **High-Yield Clinical Pearls for NEET-PG:** * **SHBG Increases in:** Hyperthyroidism, Pregnancy, Oral Contraceptive Pill (OCP) use, Cirrhosis, and Aging (in men). * **SHBG Decreases in:** Hypothyroidism, Obesity, PCOS, Hyperinsulinemia/Type 2 Diabetes, and Acromegaly. * **Clinical Correlation:** In **PCOS**, the combination of high androgens and hyperinsulinemia synergistically suppresses SHBG, making it a key marker for the disease.

Q: Inhibin is secreted by which of the following cells?

Granulosa cell. **Explanation:** **Inhibin** is a glycoprotein hormone that plays a critical role in the negative feedback regulation of the hypothalamic-pituitary-gonadal axis. Its primary function is the **selective inhibition of Follicle-Stimulating Hormone (FSH)** secretion from the anterior pituitary. 1. **Why Granulosa Cells are correct:** In females, Inhibin (specifically Inhibin B) is synthesized and secreted by the **Granulosa cells** of the developing ovarian follicles. As the follicle grows under the influence of FSH, these cells produce more Inhibin, which then feeds back to the pituitary to suppress FSH, preventing the over-stimulation of multiple follicles. (Note: In males, the functional equivalent is the **Sertoli cell**). 2. **Why other options are incorrect:** * **Theca cells:** These cells primarily produce androgens (androstenedione) under the influence of LH, which are then converted to estrogens by granulosa cells. * **Corpus luteum:** While the corpus luteum does secrete **Inhibin A** (along with progesterone and estrogen) during the luteal phase, the classic and primary source of Inhibin in the follicular phase and the most common answer for this physiological concept is the Granulosa cell. * **Decidua:** This is the modified mucosal lining of the uterus during pregnancy; it is involved in maternal-fetal exchange and hormone production (like prolactin), but not the primary secretion of Inhibin. **High-Yield Clinical Pearls for NEET-PG:** * **Inhibin B:** Marker of **ovarian reserve**; produced by small antral follicles. * **Inhibin A:** Produced by the **dominant follicle** and the **Corpus Luteum**. * **Tumor Marker:** Inhibin is a highly specific tumor marker for **Granulosa Cell Tumors** of the ovary. * **Dual Action:** While Inhibin suppresses FSH, **Activin** (also from granulosa cells) stimulates FSH secretion.

Q: Prolactin secretion is stimulated by:

TRH. **Explanation:** Prolactin (PRL) is unique among anterior pituitary hormones because its primary regulation is **inhibitory** rather than stimulatory. Under normal physiological conditions, the hypothalamus exerts a tonic inhibitory influence on prolactin via dopamine. **Why TRH is the correct answer:** Thyrotropin-Releasing Hormone (TRH), primarily known for stimulating TSH, also acts as a potent **prolactin-releasing factor**. In states of primary hypothyroidism, the lack of negative feedback leads to elevated TRH levels. This excess TRH stimulates lactotrophs in the anterior pituitary, leading to hyperprolactinemia. This explains why patients with hypothyroidism may present with galactorrhea or menstrual irregularities. **Analysis of Incorrect Options:** * **ACTH (Adrenocorticotropic Hormone):** This is a hormone secreted *by* the anterior pituitary to stimulate the adrenal cortex; it does not regulate prolactin secretion. * **GnRH (Gonadotropin-Releasing Hormone):** This stimulates the release of LH and FSH. Interestingly, high levels of prolactin actually *inhibit* GnRH secretion, leading to hypogonadism. * **Dopamine:** This is the primary **inhibitor** of prolactin (secreted via the tuberoinfundibular pathway). Drugs that block dopamine (antipsychotics) lead to increased prolactin levels. **NEET-PG High-Yield Pearls:** * **Prolactin Inhibitory Factor (PIF):** Dopamine. * **Prolactin Releasing Factors (PRF):** TRH, VIP (Vasoactive Intestinal Peptide), and Oxytocin. * **Physiological Stimuli:** Suckling (strongest), sleep, stress, and pregnancy (estrogen). * **Clinical Correlation:** Always check TSH levels in a patient with hyperprolactinemia to rule out primary hypothyroidism before considering a prolactinoma.

Q: FSH is secreted by which of the following cells?

Basophils. **Explanation:** The anterior pituitary (adenohypophysis) contains cells classified based on their staining properties with hematoxylin and eosin (H&E). **Basophils** are cells that stain with basic dyes and are responsible for secreting the "B-FLAT" hormones: **B**asophils produce **F**SH, **L**H, **A**CTH, and **T**SH. Specifically, FSH (Follicle-Stimulating Hormone) is secreted by **gonadotrophs**, which are a subtype of basophils. **Analysis of Options:** * **Option A (Chromophobes):** These are "color-hating" cells that do not pick up significant stain. They are generally considered to be either resting/degranulated acidophils/basophils or stem cells; they do not actively secrete FSH. * **Option C (Acidophils):** These stain with acidic dyes (eosin) and secrete Growth Hormone (Somatotrophs) and Prolactin (Lactotrophs). A common mnemonic is **"GPA"** (**G**rowth hormone, **P**rolactin are **A**cidophils). * **Option D (Theca interna cells):** These are ovarian cells, not pituitary cells. While they are involved in the reproductive axis, their role is to produce androgens (androstenedione) under the influence of LH, not to secrete FSH. **High-Yield Facts for NEET-PG:** * **Mnemonic for Pituitary Staining:** **"GPA"** (Acidophils: GH, Prolactin) and **"B-FLAT"** (Basophils: FSH, LH, ACTH, TSH). * **PAS Stain:** Basophils are PAS (Periodic Acid-Schiff) positive because the hormones they secrete (FSH, LH, TSH) are glycoproteins. * **Most Numerous Cell Type:** Somatotrophs (Acidophils) are the most abundant cells in the anterior pituitary. * **FSH Function:** In females, it stimulates follicular growth; in males, it acts on Sertoli cells to support spermatogenesis.

Q: Where is ADH secreted?

Supraoptic nucleus. **Explanation:** The synthesis and release of Antidiuretic Hormone (ADH), also known as Vasopressin, involve a two-step anatomical process. ADH is **synthesized** in the cell bodies of magnocellular neurons located in the hypothalamus and then **secreted** (released) into the bloodstream from the posterior pituitary. * **Why Option A is correct:** While both the Supraoptic (SON) and Paraventricular (PVN) nuclei produce both ADH and Oxytocin, the **Supraoptic nucleus** is the primary site for ADH synthesis (roughly 5/6th of ADH is produced here). In the context of NEET-PG, when forced to choose between the two, SON is the classic answer for ADH. * **Why Option B is incorrect:** The **Paraventricular nucleus** is primarily responsible for the synthesis of **Oxytocin**. Although it produces a small amount of ADH, it is not the principal site. * **Why Option C is incorrect:** The **Neurohypophysis** (Posterior Pituitary) is the site of **storage and release** into the systemic circulation via the inferior hypophyseal artery. It does not synthesize the hormone; it only houses the nerve terminals of the hypothalamo-hypophyseal tract. * **Why Option D is incorrect:** The **Adenohypophysis** (Anterior Pituitary) produces its own hormones (GH, ACTH, TSH, etc.) under the influence of hypothalamic releasing factors, but it has no role in ADH production or secretion. **High-Yield Clinical Pearls:** 1. **V1 Receptors:** Located on vascular smooth muscle (cause vasoconstriction). 2. **V2 Receptors:** Located on the **Principal cells** of the late distal tubule and collecting duct (increase water reabsorption via Aquaporin-2). 3. **Stimulus:** The most potent stimulus for ADH release is an increase in **plasma osmolarity** (detected by osmoreceptors in the OVLT), followed by a decrease in blood volume. 4. **Pathology:** Deficiency of ADH leads to **Central Diabetes Insipidus**, characterized by polyuria and low urine specific gravity.

Question 1

Which of the following hormonal concentrations decreases with age?

Accepted Answer

Growth hormone

Answer

Parathormone

Answer

FSH

Answer

Norepinephrine

Question 2

Where are the receptors for parathyroid hormone located?

Accepted Answer

Osteoblasts

Answer

Osteoclasts

Answer

Periosteum

Answer

Cartilage

Question 3

All of the following statements about adrenal glands are true EXCEPT:

Accepted Answer

The adrenal medulla normally secretes epinephrine in excess of norepinephrine.

Answer

Chromaffin granules are seen in pheochromocytoma.

Answer

Tumors of the adrenal medulla secrete epinephrine in excess of norepinephrine.

Answer

The adrenal medulla is not essential for life.

Question 4

Which of the following is NOT an endocrine function associated with the kidney?

Accepted Answer

Natriuretic peptide secretion

Answer

Erythropoietin secretion

Answer

1,25-dihydroxycholecalciferol formation

Answer

Renin secretion

Question 5

Sex hormone-binding globulin (SHBG) levels are decreased in which of the following conditions?

Accepted Answer

Increased androgen levels

Answer

Hyperthyroidism

Answer

Increased estrogen levels

Answer

Pregnancy

Question 6

Inhibin is secreted by which of the following cells?

Accepted Answer

Granulosa cell

Answer

Theca cell

Answer

Corpus luteum

Answer

Decidua

Question 7

Prolactin secretion is stimulated by:

Accepted Answer

TRH

Answer

ACTH

Answer

GnRH

Answer

Dopamine

Question 8

FSH is secreted by which of the following cells?

Accepted Answer

Basophils

Answer

Chromophobes

Answer

Acidophils

Answer

Theca interna cells

Question 9

Where is ADH secreted?

Accepted Answer

Supraoptic nucleus

Answer

Paraventricular nucleus

Answer

Neurohypophysis

Answer

Adenohypophysis

Question 10

All of the following short stature cases are caused by mechanisms independent of specific defects in the growth hormone axis, except?

Accepted Answer

Laron dwarfism

Answer

Gonadal dysgenesis

Answer

Kasper - Hauser syndrome

Answer

Achondroplasia

Endocrinology — MCQs

Endocrinology — MCQs

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