Inhibin A, Tumor Marker (INHA)

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Test Code: INHASO

Overview
Ordering
Specimen
Performing
Clinical/Interpretive
Contacts
Coding

Useful For

Aiding in the diagnosis of patients with granulosa cell tumors of the ovary when used in combination with inhibin B

Monitoring of patients with granulosa cell tumors and epithelial mucinous-type tumors of the ovary known to secrete inhibin A

Specimen Requirements

Specimen Type	Preferred Container/Tube	Acceptable Container/Tube	Specimen Volume	Specimen Minimum Volume (allows for 1 repeat)	Pediatric Minimum Volume (no repeat)
Serum	Serum Separator Tube (SST)	Red Top Tube (RTT)	0.6 mL	0.5 mL

Collection Processing Instructions

For the initial evaluation of patients suspected of having a granulosa cell tumor of the ovary, order INHAB / Inhibin A and B, Tumor Marker, Serum. If the results of the profile show that either inhibin A or B are elevated, consider monitoring the patient with the individual tests, INHA / Inhibin A, Tumor Marker, Serum or INHB / Inhibin B, Serum.

Centrifuge and aliquot serum into a plastic vial.

Specimen Stability Information

Specimen Type	Temperature	Time
Serum	Refrigerated (preferred)	14 days
	Frozen	90 days
	Ambient	7 days

Rejection Criteria

Gross hemolysis

Interference

Inhibin values fluctuate during the menstrual cycle. Inhibin levels in premenopausal women should be interpreted with caution.

Do not interpret serum inhibin levels as absolute evidence of the presence or the absence of malignant disease. Use results in conjunction with information from the clinical evaluation of the patient and other diagnostic procedures.

Tumor markers are not specific for malignancy and values may vary by testing methodology. The same method should be used to serially monitor patients.

Some patients who have been exposed to animal antigens, either in the environment or as part of treatment or imaging procedures, may have circulating anti-animal antibodies present. These antibodies may interfere with the assay reagents to produce unreliable results.

Performing Laboratory Information

Performing Location	Day(s) Test Performed	Analytical Time	Methodology/Instrumentation
Mayo Clinic Laboratories	Monday through Saturday	1 to 3 day	Immunoenzymatic Assay

Reference Lab

Mayo Clinic Laboratories

Test Information

Inhibins are heterodimeric protein hormones secreted by granulosa cells of the ovary in the female and Sertoli cells of the testis in the male. They selectively suppress the secretion of pituitary follicle stimulating hormone (FSH) and also have local paracrine actions in the gonads. The inhibins consist of a dimer of 2 homologous subunits, an alpha subunit and either a beta A or beta B subunit, to form inhibin A and inhibin B, respectively.

In females, inhibin A is primarily produced by the dominant follicle and corpus luteum: whereas inhibin B is predominantly produced by small developing follicles. Serum inhibin A and B levels fluctuate during the menstrual cycle. At menopause, with the depletion of ovarian follicles, serum inhibin A and B decrease to very low or undetectable levels.

Ovarian cancer is classified into 3 types: epithelial, stromal sex cord, and germ cell tumors. Epithelial ovarian tumors account for 90% of cases and are further subdivided into: serous (70%), mucinous (10%-15%), and endometrioid (10%-15%) types. Granulosa cell tumors represent the majority of the stromal sex cord tumors, which account for 2% to 5% of all ovarian tumors.

Elevations of serum inhibin A and B are detected in some patients with granulosa cell tumors. Inhibin A elevations have been reported in approximately 70% of granulosa cell tumors. In these patients, inhibin A levels tend to show a 6-fold to 7-fold increase over the reference range value. The frequency of elevated levels varies amongst studies, likely due to the different specificities of the antibodies used in the immunoassays.

Inhibin A also appears to be suitable markers for epithelial tumors of the mucinous type with about 20% of cases having elevated inhibin A levels. In contrast, inhibin is not a very good marker in nonmucinous epithelial tumors. At best, total inhibin is elevated in 15% to 35% of nonmucinous epithelial ovarian cancer cases.

Inhibin seems to be a complementary to cancer antigen 125 (CA 125) as an ovarian cancer marker. CA 125 is not as good of a tumor marker for mucinous and granulosa ovarian cell tumors. Inhibin shows a better performance in those 2 types of ovarian cancer.

The majority of the studies for inhibin A and B as an ovarian cancer marker have been limited to postmenopausal women where the levels for both proteins are normally very low. Inhibin A has limited utility as an ovarian cancer marker in premenopausal women, where circulating levels are higher and fluctuate throughout the menstrual cycle and, therefore, are difficult to interpret.

Reference Range Information

Males: < 5.0 pg/mL

Females

<11 years: < 5.0 pg/mL

11-17 years: < 98 pg/mL

Premenopausal: < 98 pg/mL

Postmenopausal: < 5.0 pg/mL

Interpretation

Inhibin A levels are elevated in approximately 70% of patients with granulosa cell tumors and in approximately 20% of patients with epithelial ovarian tumors. A normal inhibin A level does not rule-out a mucinous or granulosa ovarian cell tumor. Testing for inhibin B in these cases might be informative as a higher proportion of mucinous or granulosa ovarian cell tumors will have an elevated inhibin B level. Consider ordering INHAB/Inhibin A and B, Tumor Marker, Serum.

For monitoring of patients with known ovarian cancer, inhibin A levels decrease shortly after surgery. Elevations of inhibin A after treatment are suggestive of residual, recurrent, or progressive disease. In patients with recurrent disease, inhibin A elevation seems to be present earlier than clinical symptoms. Patients in remission show normal levels of inhibin A.

Outreach CPTs

CPT	Modifier (if needed)	Quantity	Description	Comments
86336

Ordering Applications

Ordering Application	Description
Cerner	Inhibin A, Tumor Marker (INHA)

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