Alpha Subunit (HCG, TSH, FSH, LH) (Sendout)

Interpretation

Method

Immunochemiluminescent Assay

Reference Range

Units: ng/mL

Female		Male
Age	Range	Age	Range
1d-5d	0.0-50.0	None	None
6d-2m	0.0-10.0	None	None
3m-	0.0-1.2	None	None

Effective date: 09/08/2022

Ref. Range Notes

Reference Values, Adult Females:

Premenopausal Females:	< or = 1.2 ng/mL
Postmenopausal Females:	< or = 1.8 ng/mL

Pediatric and adult reference values based on Mayo studies.

Puberty onset (transition from Tanner stage I to Tanner stage II) occurs for boys at a median age of 11.5 (+/-2) years and for girls at a median age of 10.5 (+/-2) years. There is evidence that it may occur up to 1 year earlier in obese girls and in African American girls. For boys, there is no proven relationship between puberty onset and body weight or ethnic origin. Progression through Tanner stages is variable. Tanner stage V (adult) should be reached by age 18.

Interpretation:

In the case of pituitary adenomas that do not produce significant amounts of intact tropic hormones, diagnostic differentiation between sellar- and tumors of non-pituitary origin (eg, meningiomas or craniopharyngiomas) can be difficult. In addition, if such nonsecreting adenomas are very small, they can be difficult to distinguish from physiological pituitary enlargements.

In a proportion of these cases, free alpha-subunit may be elevated, aiding in diagnosis. Overall, 5% to 30% of pituitary adenomas produce measurable elevation in serum free alpha-subunit concentrations. There is also evidence that an exuberant free alpha-subunit response to thyrotropin-releasing hormone (TRH) administration may occur in some pituitary adenoma patients that do not have elevated baseline free alpha-subunit levels. A more than 2-fold increase in free alpha-subunit serum concentrations at 30 to 60 minutes following intravenous administration of 500 mcg of TRH is generally considered abnormal, but some investigators consider any increase of serum free alpha-subunit that exceeds the reference range as abnormal. TRH testing is not performed in the laboratory but in specialized clinical testing units under the supervision of a physician.

In pituitary tumors patients with pre-treatment elevations of serum free alpha-subunit, successful treatment is associated with a reduction of serum free alpha-subunit levels. Failure to lower levels into the normal reference range may indicate incomplete cure, and secondary rises in serum free alpha-subunit levels can indicate tumor recurrence.

Small thyrotropin (TSH)-secreting pituitary tumors are difficult to distinguish from thyroid hormone resistance. Both types of patients may appear clinically euthyroid or mildly hyperthyroid and may have mild-to-modest elevations in peripheral thyroid hormone levels along with inappropriately (for the thyroid hormone level) detectable TSH, or mildly-to-modestly elevated TSH. Elevated serum free alpha-subunit levels in such patients suggest a TSH secreting tumor, but genetic variant screening of the thyroid hormone receptor gene may be necessary for a definitive diagnosis.

Constitutional delay of puberty (CDP) is a benign, often familial condition in which puberty onset is significantly delayed but eventually occurs and then proceeds normally. By contrast, hypogonadotrophic hypogonadism (HH) represents a disease state characterized by lack of gonadotropin production. Its causes are varied, ranging from idiopathic over specific genetic abnormalities to hypothalamic and pituitary inflammatory or neoplastic disorders. In children, it results in complete failure to enter puberty without medical intervention. CDP and HH can be extremely difficult to distinguish from each other. Intravenous administration of 100 mcg gonadotropin releasing hormone (GnRH) results in much more substantial rise in free alpha-subunit levels in CDP patients, compared with HH patients. A greater than 6-fold rise at 30 or 60 minutes post-injection is seen in more than 75% of patients with CDP, while a less than 2-fold rise appears diagnostic of HH. Increments between 2- and 6-fold are nondiagnostic.

GnRH testing is not performed in the laboratory but in specialized clinical testing units under the supervision of a physician.

Interferences and Limitations

Cautions:

False-positive elevations in serum free alpha-subunit levels may be seen in some women if blood specimens are drawn within 24 hours of ovulation.

Patients with end-stage renal failure may have serum free alpha-subunit concentrations of up to 6-times the upper limit of reference range.

Elevated alpha-subunit results on patients with elevated thyrotropin (TSH) should be interpreted with caution due to TSH cross-reactivity with the assay.

Assisted reproduction involving ovarian hyperstimulation or in vitro fertilization may be associated with the elevation in serum free alpha-subunit levels.

Pregnancy is associated with very substantial, physiological elevations in serum free alpha-subunit levels, paralleling chorionic gonadotropin (hCG) secretion. This test should not be ordered on pregnant patients.

Ordering & Collection

Specimen Type

Blood

Collection

3 mL blood in GOLD SST or RED TOP tube

Handling Instructions

Outside Laboratories: Centrifuge sample and transfer serum to a separate plastic vial. Freeze serum at -20°C while awaiting shipment. Transport samples on dry ice.

Stability: Frozen (preferred): 90 days; Refrigerated: 7 days; Ambient: Unacceptable.

Reject Due To: Gross hemolysis. Gross lipemia, gross icterus is acceptable.

Quantity

Requested: 1 mL serum
Minimum: 0.2 mL serum

Processing

Receiving Instructions

Centrifuge sample and transfer serum to a separate plastic vial. Freeze serum at -20°C.

Sendouts:

• Order Mayo Test: APGH.
• Interfaced: Yes.

Stability: Frozen (preferred): 90 days; Refrigerated: 7 days; Ambient: Unacceptable.

Reject Due To: Gross hemolysis. Gross lipemia, gross icterus is acceptable.

Misc Sendout

Performance

Lab Department

Sendouts Mayo Lab (FZ)(MAFZ)

Frequency

Performed: Sunday. Report Available: 2-8 days.

Available STAT?

No

Performing Location(s)

Sendout	Mayo Clinic Laboratories (Superior Drive) 800-533-1710 3050 Superior Drive NW Rochester, MN 55901

Billing & Coding

CPT Codes

83520

LOINC

14170-5

Interfaced Order Code

UOW5257

Interfaced Result Code

UOW5257