Reference Interval SI Units

856 nmol/L 193-690

Magnetic resonance imaging (MRI) of the pituitary was next carried out in search of a pituitary adenoma with and without gadolinium contrast enhancement. The MRI report is summarized as follows: "Overall, the pituitary gland did not appear definitively enlarged. There was a suggestion of asymmetry and prominence of the left side of the gland when compared to the right. The gadolinium-enhanced scan demonstrated a fairly homogeneous contrast enhancement except for a questionable small (~5 mm) focus of slightly increased signal in the most anterior left portion of the pituitary. However, there was no definite evidence for pituitary microadenoma."

If imaging had revealed an adenoma, the diagnosis of Cushing disease would have been established. In the absence of definitive MRI evidence of a pituitary adenoma, inferior petrosal venous sinus sampling (IPSS) was carried out in radiology. Results are listed in Table 21.1.

At baseline (—15 minutes and 0 minute), the IPSS-R sample is more than 10 fold greater than the peripheral and the IPSS-L concentrations. The magnitude of these differences was amplified by CRH injection. IPSS to peripheral blood ACTH ratios of > 3 are consistent with a pituitary source of the ACTH. The average ratio of IPSS ACTH to peripheral ACTH in Cushing disease is 15 with the lower limit of normal near 1.5-1.7. These data are consistent with an ACTH-secreting pituitary adenoma even in the presence of ambivalent MRI findings.

Review of the clinical and laboratory data supported the diagnosis of Cushing disease: lymphopenia, eosinopenia, and hypokalemia, and a metabolic alkalosis with hypertension, fasting hyperglycemia and reduced bone mineral density.

Neurosurgery was consulted. Prior to surgery her hypertension was managed with benazepril HCl and hydrochlorothiazide. Benazepril HCl is an angiotensin-converting enzyme inhibitor, whereas hydrochlorothiazide is a diuretic.

Transplenoidal removal of a ~4-mm pituitary mass was accomplished. The tumor was localized to the right side of the pituitary gland. Immunohistochemistry was positive for ACTH staining in the microadenoma.

The patient's postoperative course was unremarkable. From 6 weeks to 12 weeks postoperatively she was weaned off replacement doses of oral glucocorticoids. Over the next year, regular menses returned, she was weaned off her antihypertensives, she lost weight and her psychological disposition improved.

Table 21.1 Corticotropin-Releasing Hormone (CRH) Stimulation Test

ACTH

ACTH

ACTH

ACTH

ACTH

ACTH

ratio:

ratio:

Cortisol

(pg/mL)

(pg/mL)

(pg/mL)

ratio: IPSS-R/

IPSS-L/

IPSS-

(mg/dL)

Time

peripheral

IPSS-Ra

IPSS-Lb

peripheral

peripheral

R/IPSS-L pheripheral

-15

15

170

13

11.3

0.87

13.1

10

0

20

285

18

14.2

0.90

15.8

8.8

+ 3

21

836

48

39.8

2.3

17.4

8.3

+5

40

729

78

18.2

1.95

9.3

7.5

+ 10

45

585

56

13.0

1.24

10.4

12.6

+ 15

70

747

81

10.7

1.16

9.2

18.8

+ 30

94

797

105

8.5

1.12

7.6

26.3

+60

132

784

221

5.9

1.67

3.5

30.8

aIPSS-R = right inferior petrosal venous sinus sample. bIPSS-L = left inferior petrosal venous sinus sample. Note: ACTH pg/mL x 0.22 = ACTH pmol/L.

aIPSS-R = right inferior petrosal venous sinus sample. bIPSS-L = left inferior petrosal venous sinus sample. Note: ACTH pg/mL x 0.22 = ACTH pmol/L.

Was this article helpful?

0 0
How To Deal With Rosacea and Eczema

How To Deal With Rosacea and Eczema

Rosacea and Eczema are two skin conditions that are fairly commonly found throughout the world. Each of them is characterized by different features, and can be both discomfiting as well as result in undesirable appearance features. In a nutshell, theyre problems that many would want to deal with.

Get My Free Ebook


Post a comment