Endocrine pathology Practice Questions

Q: A 28-year-old man presents with polyuria (6 liters/day), polydipsia, and nocturia for 2 months. He has no significant medical history. Serum sodium is 148 mEq/L, serum osmolality 305 mOsm/kg, and urine osmolality 180 mOsm/kg. After 8-hour water deprivation, urine osmolality increases to 250 mOsm/kg. Following administration of desmopressin, urine osmolality increases to 650 mOsm/kg. Apply this data to determine the diagnosis.

Central diabetes insipidus. ***Central diabetes insipidus*** - The significant increase in **urine osmolality** (>50% and reaching 650 mOsm/kg) after **desmopressin** administration confirms that the kidneys are responsive to ADH, but the body is not producing it. - Preliminary findings of **hypernatremia** and high **serum osmolality** with dilute urine indicate a failure of the **hypothalamic-pituitary axis** to release antidiuretic hormone. *Osmotic diuresis from diabetes mellitus* - This condition would present with high **urine osmolality** (usually >300 mOsm/kg) due to the presence of **glucose** or other solutes. - The patient's low initial urine osmolality (180 mOsm/kg) and the dramatic response to ADH are inconsistent with a **solute-driven** diuresis. *Diabetes insipidus with partial nephrogenic component* - A partial nephrogenic component would show a blunt or **incomplete response** to exogenous desmopressin, rather than a normalize concentration. - The patient's urine osmolality reached 650 mOsm/kg, which demonstrates a robust and **intact renal response** to ADH analogs. *Nephrogenic diabetes insipidus* - In this condition, the kidneys are resistant to ADH, so there would be **minimal to no change** in urine osmolality after giving desmopressin. - The patient’s urine osmolality more than doubled following **desmopressin**, effectively ruling out a primary **renal tubule defect**. *Primary polydipsia* - Patients with primary polydipsia typically have **hyponatremia** and low serum osmolality due to excessive free water intake. - During a **water deprivation test**, these patients are generally able to concentrate their urine significantly (often >600 mOsm/kg) without needing exogenous hormones.

Q: A 32-year-old woman with a history of postpartum hemorrhage 18 months ago presents with fatigue, cold intolerance, and inability to lactate after delivery. She reports having no menstrual periods since delivery and has gained 15 pounds. Laboratory studies show low TSH, low free T4, low cortisol, and low estradiol. Apply your knowledge to determine the underlying pathologic process.

Pituitary infarction from severe postpartum hypotension. ***Pituitary infarction from severe postpartum hypotension*** - This patient presents with **Sheehan syndrome**, which is ischemic necrosis of the **anterior pituitary** caused by severe **postpartum hemorrhage** and hypotension. - The deficiency of multiple hormones (**TSH, ACTH, Prolactin, Gonadotropins**) explains her fatigue, cold intolerance, failure to lactate, and secondary **amenorrhea**. *Hypothalamic dysfunction from psychological stress* - Stress-induced hypothalamic dysfunction typically leads to **functional hypothalamic amenorrhea**, but it does not cause **hypothyroidism** or profound **hypocortisolism**. - It would not explain the inability to lactate or the specific history of severe **obstetric hemorrhage**. *Primary adrenal insufficiency with secondary amenorrhea* - Primary adrenal insufficiency would typically present with **elevated ACTH** (leading to hyperpigmentation) rather than the low cortisol and low ACTH/TSH seen here. - It does not account for the **low TSH** and **failure to lactate**, which point to a central pituitary defect. *Autoimmune polyglandular syndrome type 2* - This syndrome usually involves **Primary Adrenal Insufficiency (Addison's)** and autoimmune thyroid disease, which would show **elevated TSH** or ACTH levels. - It is not associated with **postpartum hemorrhage** and would not cause the panhypopituitarism described. *Primary hypothyroidism with concurrent ovarian failure* - Primary hypothyroidism would result in an **elevated TSH** level as the pituitary attempts to compensate for low thyroid hormone. - Primary ovarian failure would present with **elevated FSH and LH** (hypergonadotropic hypogonadism) rather than the low estradiol and amenorrhea seen in pituitary failure.

Q: A 50-year-old lady with thyroid swelling underwent total thyroidectomy. The gross specimen and histopathological slide is shown below. Diagnosis is:

Medullary carcinoma of thyroid. ***Medullary carcinoma of thyroid*** - The gross specimen of medullary carcinoma often shows a **firm, grey-white, ill-defined mass**, which can be seen in the provided image. - Histopathologically, it is characterized by nests or cords of **polygonal or spindle cells** with **amyloid deposition** in the stroma, which stains positive with Congo red. *Hashimoto thyroiditis* - Grossly, Hashimoto thyroiditis typically presents as a **diffusely enlarged, firm, pale gland**, not a discrete mass. - Histologically, it is characterized by **lymphocytic infiltration**, **germinal centers**, and **Hurthle cell change**, without amyloid deposition or the specific cellular architecture of medullary carcinoma. *Follicular carcinoma* - Grossly, follicular carcinoma often appears as a **solitary, well-circumscribed nodule** with a fibrous capsule, which may show areas of hemorrhage or necrosis [1]. - Histologically, the diagnosis of follicular carcinoma relies on evidence of **capsular and/or vascular invasion** by follicular cells, which is not the primary feature suggested by the image [1]. *Anaplastic carcinoma* - Grossly, anaplastic carcinoma is typically a **rapidly growing, large, invasive mass** that often extends beyond the thyroid capsule [2]. - Histologically, it is characterized by highly **pleomorphic, bizarre giant cells** and/or spindle cells with frequent mitoses and necrosis, lacking the specific features of medullary carcinoma [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1100-1101. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1101-1102.

Question 1

A 28-year-old man presents with polyuria (6 liters/day), polydipsia, and nocturia for 2 months. He has no significant medical history. Serum sodium is 148 mEq/L, serum osmolality 305 mOsm/kg, and urine osmolality 180 mOsm/kg. After 8-hour water deprivation, urine osmolality increases to 250 mOsm/kg. Following administration of desmopressin, urine osmolality increases to 650 mOsm/kg. Apply this data to determine the diagnosis.

Accepted Answer

Central diabetes insipidus

Answer

Osmotic diuresis from diabetes mellitus

Answer

Diabetes insipidus with partial nephrogenic component

Answer

Nephrogenic diabetes insipidus

Answer

Primary polydipsia

Question 2

A 32-year-old woman with a history of postpartum hemorrhage 18 months ago presents with fatigue, cold intolerance, and inability to lactate after delivery. She reports having no menstrual periods since delivery and has gained 15 pounds. Laboratory studies show low TSH, low free T4, low cortisol, and low estradiol. Apply your knowledge to determine the underlying pathologic process.

Accepted Answer

Pituitary infarction from severe postpartum hypotension

Answer

Hypothalamic dysfunction from psychological stress

Answer

Primary adrenal insufficiency with secondary amenorrhea

Answer

Autoimmune polyglandular syndrome type 2

Answer

Primary hypothyroidism with concurrent ovarian failure

Question 3

A 45-year-old woman presents with a 3-month history of heat intolerance, weight loss, and palpitations. Physical examination reveals exophthalmos, diffuse thyroid enlargement, and a fine tremor. Laboratory studies show TSH <0.01 mIU/L (normal: 0.4-4.0), free T4 6.8 ng/dL (normal: 0.8-1.8), and positive TSH receptor antibodies. A thyroid ultrasound shows diffuse enlargement with increased vascularity. Apply the pathophysiologic mechanism to explain her ocular findings.

Accepted Answer

Autoimmune inflammation and glycosaminoglycan deposition in retro-orbital tissues

Answer

Sympathetic hyperactivity causing lid retraction only

Answer

Hyperthyroid-induced increased intraocular pressure

Answer

Compression of orbital veins by enlarged thyroid gland

Answer

Direct infiltration of orbital muscles by thyroid tissue

Question 4

A 50-year-old lady with thyroid swelling underwent total thyroidectomy. The gross specimen and histopathological slide is shown below. Diagnosis is:

Accepted Answer

Medullary carcinoma of thyroid

Answer

Hashimoto thyroiditis

Answer

Follicular carcinoma

Answer

Anaplastic carcinoma

Answer

Papillary carcinoma

Endocrine pathology — MCQs

Endocrine pathology — MCQs

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