Cushing Disease: ACTH-Producing Pituitary Lesion
The answer is c. ACTH-producing pituitary lesion. Cushing disease is specifically defined as hypercortisolism caused by an ACTH-secreting pituitary adenoma 1, 2, 3.
Pathophysiology
Cushing disease results from a benign monoclonal pituitary adenoma that secretes excessive adrenocorticotropic hormone (ACTH), which in turn stimulates the adrenal glands to produce supraphysiological levels of cortisol 3. This represents the most common cause of endogenous Cushing's syndrome, accounting for approximately 70% of adult cases 2, 4.
Histologic Variants
The pathologic spectrum includes 5:
- Basophilic microadenomas (most frequent)
- Chromophobic macroadenomas
- Crooke's cell adenomas
- Corticotroph carcinomas (rare)
- Corticotroph hyperplasia (documented in approximately 20% of cases, particularly relevant in MRI-negative disease) 6
Important caveat: In some cases, no tumor can be identified on imaging despite biochemical confirmation of pituitary-dependent disease. MRI-negative Cushing disease occurs in a significant subset of patients and shows lower surgical remission rates (70%) compared to MRI-positive cases (82%) 6.
Why Other Options Are Incorrect
- Pituitary apoplexy (option a): This is acute hemorrhage or infarction of a pituitary tumor, not a cause of Cushing disease
- Arginine vasopressin disorder (option b): This relates to diabetes insipidus or SIADH, not cortisol excess
- Empty sella syndrome (option d): This represents absence or compression of pituitary tissue, not ACTH hypersecretion
Prolactinoma in Females: Oligomenorrhea
The answer is a. Oligomenorrhea. This is the hallmark presenting feature of prolactinoma in women of reproductive age.
Elevated prolactin suppresses gonadotropin-releasing hormone (GnRH) pulsatility, leading to hypogonadotropic hypogonadism. This manifests as:
- Oligomenorrhea or amenorrhea
- Galactorrhea
- Infertility
- Decreased libido
Visual disturbances (option b) occur with macroadenomas causing mass effect but are not the typical presenting feature in women, who usually present earlier due to menstrual irregularities. Obesity and polydipsia are not characteristic features of prolactinomas.
Hyperprolactinemia Management: Dopamine Receptor Agonists
The answer is d. Dopamine receptor agonists. These are first-line pharmacologic therapy for hyperprolactinemia across all pituitary conditions causing elevated prolactin.
Dopamine physiologically inhibits prolactin secretion from lactotroph cells. Dopamine agonists (cabergoline, bromocriptine) effectively:
- Normalize prolactin levels
- Restore gonadal function
- Reduce tumor size
Cabergoline is preferred over bromocriptine due to superior efficacy, tolerability, and twice-weekly dosing. In the context of Cushing disease, cabergoline has shown biochemical normalization in 25-40% of patients in small studies, though sustained control occurs in only 23% long-term 1. The medication has been used safely in pregnancy for prolactinomas.
Important monitoring: Cabergoline-induced impulse-control disorders (hypersexuality, pathological gambling, excessive alcohol consumption, overeating) are likely under-reported and require clinical vigilance 1.
The other options target different pathways:
- Somatostatin analogs (option a): Used for acromegaly and some cases of Cushing disease (pasireotide)
- Growth hormone receptor inhibitors (option b): Used for acromegaly (pegvisomant)
- Glucocorticoid receptor antagonists (option c): Used for Cushing syndrome (mifepristone)
Confidence Assessment Questions
Questions 4 and 5 are self-assessment items without correct/incorrect answers. They evaluate the clinician's subjective confidence level in:
- Recognizing hallmark signs and symptoms of pituitary conditions
- Treating pituitary disorders with pharmacotherapy
These questions serve educational needs assessment purposes rather than testing medical knowledge.