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26259 Alpha-Subunit Pituitary Tumor Marker, Serum (APGH)

Alpha-Subunit Pituitary Tumor Marker, Serum (APGH)
Test Code: APGHSO
Synonyms/Keywords

​Alpha Glycoprotein Subunit
Alpha Subunit, HCG
Alpha-HCG (Human Chorionic Gonadotropin)
Alpha-PGH (Pituitary Glycoprotein Hormone)
Alpha-Subunit of Pituitary Glycoprotein Hormones (Alpha-PGH), Serum
Chorionic Gonadotropins, Alpha-Subunit
Glycoprotein Subunit
HCG, Alpha Subunit
Hormone, Alpha-Subunit
PGH (Pituitary Glycoprotein Hormone)
Pituitary Glycoprotein Alpha Subunit
Pituitary Gonadotropins, Alpha-Subunit

Useful For

Adjunct in the diagnosis of pituitary tumors

As part of the follow-up of treated pituitary tumor patients

Differential diagnosis of thyrotropin-secreting pituitary tumor versus thyroid hormone resistance

Differential diagnosis of constitutional delay of puberty versus hypogonadotrophic hypogonadism

Specimen Requirements
Specimen TypePreferred Container/TubeAcceptable Container/TubeSpecimen VolumeSpecimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
​Serum​Serum Separator Tube (SST)​Red Top Tube (RTT)​1 mL​0.35 mL
Specimen Stability Information
Specimen TypeTemperatureTime
​Serum​Frozen (preferred)​90 days
​Refrigerated​7 days
Rejection Criteria
Gross Hemolysis
Interference

​This test should not be ordered on pregnant patients.

Performing Laboratory Information
Performing LocationDay(s) Test PerformedReport AvailableMethodology/Instrumentation
​Mayo Clinic Laboratories​Monday​1 to 7 days​Immunochemiluminescent Assay
Reference Lab
Reference Range Information
Performing LocationReference Range
​Mayo Clinic Laboratories

PEDIATRIC

< or =5 days: < or =50 ng/mL

6 days-12 weeks: < or =10 ng/mL

3 months-17 years: < or =1.2 ng/mL

Tanner II-IV*: < or =1.2 ng/mL

 

ADULTS

Males: < or =0.5 ng/mL

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 CDP patients, 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. 

Outreach CPTs
CPTModifier
(if needed)
QuantityDescriptionComments
​82397​1
Synonyms/Keywords

​Alpha Glycoprotein Subunit
Alpha Subunit, HCG
Alpha-HCG (Human Chorionic Gonadotropin)
Alpha-PGH (Pituitary Glycoprotein Hormone)
Alpha-Subunit of Pituitary Glycoprotein Hormones (Alpha-PGH), Serum
Chorionic Gonadotropins, Alpha-Subunit
Glycoprotein Subunit
HCG, Alpha Subunit
Hormone, Alpha-Subunit
PGH (Pituitary Glycoprotein Hormone)
Pituitary Glycoprotein Alpha Subunit
Pituitary Gonadotropins, Alpha-Subunit

Ordering Applications
Ordering ApplicationDescription
​COM​AlphaSubPituitary Tumor Marker
​Cerner​Alpha-Subun Pituitary T (APGH)
​Centricity​Alpha-Subun Pituitary T (APGH
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Specimen TypePreferred Container/TubeAcceptable Container/TubeSpecimen VolumeSpecimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
​Serum​Serum Separator Tube (SST)​Red Top Tube (RTT)​1 mL​0.35 mL
Specimen Stability Information
Specimen TypeTemperatureTime
​Serum​Frozen (preferred)​90 days
​Refrigerated​7 days
Rejection Criteria
Gross Hemolysis
Interference

​This test should not be ordered on pregnant patients.

Useful For

Adjunct in the diagnosis of pituitary tumors

As part of the follow-up of treated pituitary tumor patients

Differential diagnosis of thyrotropin-secreting pituitary tumor versus thyroid hormone resistance

Differential diagnosis of constitutional delay of puberty versus hypogonadotrophic hypogonadism

Reference Range Information
Performing LocationReference Range
​Mayo Clinic Laboratories

PEDIATRIC

< or =5 days: < or =50 ng/mL

6 days-12 weeks: < or =10 ng/mL

3 months-17 years: < or =1.2 ng/mL

Tanner II-IV*: < or =1.2 ng/mL

 

ADULTS

Males: < or =0.5 ng/mL

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 CDP patients, 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. 

For more information visit:
Performing Laboratory Information
Performing LocationDay(s) Test PerformedReport AvailableMethodology/Instrumentation
​Mayo Clinic Laboratories​Monday​1 to 7 days​Immunochemiluminescent Assay
Reference Lab
For billing questions, see Contacts
Outreach CPTs
CPTModifier
(if needed)
QuantityDescriptionComments
​82397​1
For most current information refer to the Marshfield Laboratory online reference manual.