We’re back with a USMLE® Step 2 CK Question of the Day! Today’s case involves a 45-year-old man with morning headaches who underwent bilateral adrenalectomy to treat his Cushing syndrome. Which of the following is the next best step in management?
A 45-year-old man comes to his outpatient provider because of headaches and changes in vision that began one-month ago. The headaches are worse in the morning and improve over the day. Past medical history is notable for Cushing syndrome refractory to medical treatment, for which the patient underwent bilateral adrenalectomy seven months ago. He was prescribed hydrocortisone supplements after the surgery but has been inconsistent in taking his medications. In the office, his temperature is 37.8°C (100.0°F) and blood pressure is 120/79 mmHg. Physical examination is notable for hyperpigmentation of the skin. Visual field testing reveals bitemporal hemianopsia. Laboratory testing is notable for a serum ACTH of 700 pg/mL. Magnetic resonance imaging confirms the patient’s underlying condition. Which of the following is the next best step in management?
A. Initiation of dexamethasone supplementation
B. Transsphenoidal resection of the pituitary gland
C. Initiation of octreotide therapy
D. Resection of the hypothalamus
E. Initiation of chemotherapyScroll down for the correct answer!
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The correct answer to today’s USMLE® Step 2 CK Question is…
B. Transsphenoidal resection of the pituitary gland
Before we get to the Main Explanation, let’s see why the answer wasn’t A, C, D or E. Skip to the bottom if you want to see the correct answer right away!
Incorrect answer explanations
Today’s incorrect answers are…
A. Initiation of dexamethasone supplementation
Incorrect: Patients who have undergone bilateral adrenalectomy should take glucocorticoid supplements. This helps prevent the symptoms of adrenal insufficiency. In contrast, this patient’s symptoms of morning headaches and visual disturbances are most consistent with Nelson syndrome (post-adrenalectomy enlargement of the pituitary gland). Glucocorticoid supplements are ineffective in treating Nelson syndrome.
C. Initiation of octreotide therapy
Incorrect: Octreotide can be used to treat acromegaly and gigantism in patients with growth hormone-secreting pituitary adenomas. However, there is little data supporting the efficacy of octreotide in treating the ACTH-secreting pituitary adenomas found in patients with Nelson syndrome.
D. Resection of the hypothalamus
Incorrect: The patient’s symptom of bitemporal hemianopsia is suggestive of a pituitary adenoma that is compressing the optic chiasm. Surgical intervention should be focused on resecting the enlarged pituitary and not the hypothalamus.
E. Initiation of chemotherapy
Incorrect: A pituitary adenoma can compress the optic chiasm and cause bitemporal hemianopsia. However, adenomas are benign tumors. Chemotherapy is not indicated in the treatment of pituitary adenomas, and it can lead to severe side-effects in the patient.
Main Explanation
This patient has Nelson syndrome, which is a condition in which the pituitary gland enlarges after bilateral adrenalectomy. Bilateral adrenalectomy can be performed to treat Cushing syndrome in patients who have failed more conservative treatment options.
The pathophysiology of Nelson syndrome is not fully understood. However, one proposed mechanism is that after the bilateral adrenal glands are excised, there is removal of negative-feedback to the hypothalamus and pituitary, since endogenous cortisol is no longer being synthesized. This results in increased corticotropin-releasing hormone (CRH) from the hypothalamus. The elevated CRH subsequently increases ACTH production by the pituitary gland. Overtime, the result is pituitary enlargement. In addition, since ACTH and melanocyte stimulating hormone (MSH) are derived from the same precursor molecule, increased ACTH production would also lead to increased MSH production.
The enlarged pituitary can compress nearby nerves and cause headaches. Moreover, the enlarged pituitary can compress the optic chiasm and cause bitemporal hemianopsia. Patients can also have skin hyperpigmentation secondary to increased MSH production.
Surgical resection of the pituitary is the first-line treatment of Nelson syndrome. Radiotherapy or radiosurgery can be utilized in patients who have failed first-line treatment. Medications such as bromocriptine and cabergoline have been tested, but these are generally not as effective as surgical intervention.
Major Takeaway
Nelson syndrome refers to pituitary gland enlargement after bilateral adrenalectomy. This is thought to be because removal of the adrenal glands eliminates negative feedback to the hypothalamus. Nelson syndrome can present with headaches, visual impairments, and hyperpigmentation. First-line treatment is surgical resection of the pituitary.
References
Carlstrom, L.P., Graffeo, C.S., Perry, A., Stokken, J.K., Van Gompel, J.J. (2019) Nelson-Salassa syndrome progressing to pituitary carcinoma: A case report and review of the literature. Cureus. 11(9), e5595. Doi: 10.7759/cureus.5595.
“Nelson Syndrome.” National Organization for Rare Disorders. Web Address: https://rarediseases.org/rare-diseases/nelson-syndrome/.
Patel, J., Eloy, J.A., Liu, J.K. (2015) Nelson’s syndrome: A review of the clinical manifestations, pathophysiology, and treatment strategies. Neurosurgical Focus. 38(24), E14. Doi: 10.3171/2014.10.FOCUS14681.
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