Corticotropin-Dependent Cushing Syndrome: When Inferior Petrosal Sinus Sampling Is Not Needed

Most patients with corticotropin (ACTH)-dependent Cushing syndrome (CS) will have an ACTH-secreting pituitary tumor. When a clear-cut pituitary tumor is found on magnetic resonance imaging (MRI) in a woman with slowly progressive and mild-to-moderate ACTH-dependent CS, proceeding directly to transsphenoidal pituitary surgery (TSS) is a reasonable next step. Herein we present such a case in which inferior petrosal sinus sampling (IPSS) was not needed.

Case Report

The patient was a 26-year-old woman who was referred for a second opinion on whether she might have CS. She developed very subtle signs and symptoms of glucocorticoid excess over the past 2 1/2 years. With plans for fertility, she stopped her oral contraceptive pill 3 years ago and has not had a menstrual period since. She sought consultation with a reproductive endocrinologist, and the serum prolactin concentration was normal, but the serum dehydroepiandrosterone sulfate (DHEA-S) concentration was elevated ( Table 56.1 ). Her symptoms included insomnia (routinely woke between 11:30 pm and 1:30 am and she felt “wired”), new-onset acne, mild hirsutism, and a 10-pound weight gain with distribution above her clavicles, in her face, and on her abdomen. She was diagnosed with new-onset hypertension 1 year ago. She had been working hard to prevent further weight gain with a high-intensity exercise program 5 days a week for 45 minutes. Her only medication was α-methyldopa, 500 mg daily. On physical examination her body mass index was 21.8 kg/m ² , blood pressure was 138/97 mmHg, and heart rate 96 beats per minute. She did not appear overtly cushingoid. Her skin was normal and there were no purple-red striae. Her abdomen was flat. Compared to her old photographs, she did have supraclavicular fullness ( Fig. 56.1 ). She had good muscle tone and no proximal muscle weakness.

TABLE 56.1

Laboratory Tests

Biochemical Test	Result	Repeat Test Result	Repeat Test Result	Reference Range
Sodium, mEq/L	142			135–145
Potassium, mEq/L	4.0			3.6–5.2
Fasting plasma glucose, mg/dL	85			70–100
Glycosylated hemoglobin, %	5.2			4–6
Creatinine, mg/dL	0.7			0.6–1.1
eGFR, mL/min per BSA	>60			>60
8 am serum cortisol, mcg/dL	23	15	22.9	7–25
4 pm serum cortisol, mcg/dL	14			2–14
24-Hour UFC, mcg	111	296	103	3.5–45
24-Hour urine volume, L	3.7	2.4	3.1	Goal <4 L
Late night salivary cortisol, ng/dL	190	210		≤100
ACTH, pg/mL	80	50	88	10–60
DHEA-S, mcg/dL	687	502	561	44–332
Prolactin, ng/mL	10			3–27
8-mg overnight DST, mcg/dL	2.1			Undetectable