What is the role of hormone measurement in the diagnosis of McCune-Albright syndrome?

Updated: Jan 17, 2019
  • Author: Gabriel I Uwaifo, MD; Chief Editor: George T Griffing, MD  more...
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Answer

In patients with sexual precocity, baseline gonadotropin (ie, LH and FSH) and gonadotropin levels stimulated by gonadotropin-releasing hormone (GnRH) are below normal limits. In females who are affected, estrogen levels are elevated above the age-adjusted expected level. Similarly, males who are affected have elevated serum free and total testosterone levels. Androgen levels in female patients remain within normal limits.

Precocious puberty in MAS is gonadotropin-independent. Therefore, the finding of elevated estradiol levels and suppressed or undetectable gonadotropin levels is diagnostic of gonadotropin-independent puberty. However, estrogen secretion is frequently episodic in MAS; thus, multiple assays over time may be necessary to demonstrate an elevation in estradiol levels.

Because secretion of LH and FSH is pulsatile, random gonadotropin levels in early puberty are often equal to prepubertal levels. Additionally, significant pulses may only occur at night in early puberty. An LH-releasing hormone (LH-RH) stimulation test (gonadorelin hydrochloride 100 mg intravenously [IV]) can help to differentiate between central gonadotropin-dependent and gonadotropin-independent precocious puberty.

In this test, serum is sampled for LH and FSH at 0 minutes, 15 minutes, 30 minutes, 45 minutes, and 60 minutes after administration of LH-RH. Suppressed or undetectable levels of LH and FSH after administration of LH-RH are consistent with MAS.


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