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PubMed This is a summary of 23 peer-reviewed journal articles Updated
Endocrinology

Endocrine Management: Balancing the Body's Hormones

At a Glance

McCune-Albright syndrome can cause several hormone problems, including early puberty, growth hormone excess, hyperthyroidism, and phosphate wasting. Care combines regular blood tests and imaging with individualized medicines or surgery to protect bone growth and health.

In McCune-Albright Syndrome (MAS), the genetic mutation acts like an “on” switch stuck in various glands. This means your body may produce too much of several different hormones. Because these hormones directly affect how your bones grow and strengthen, managing the endocrine system is a critical part of treating the whole person [1][2].

Precocious Puberty: Managing Early Development

Precocious (early) puberty is often the most visible endocrine sign of MAS, especially in girls, though boys can also have testicular lesions that autonomously produce testosterone. It is caused by autonomous peripheral glands (like ovarian cysts) that release hormones on their own, regardless of signals from the brain [3][4].

  • The Goal: Treatment aims to manage early physical changes (like bleeding or breast development) and, more importantly, to slow down bone age advancement. If the bones mature too quickly, the “growth plates” close early, which can lead to a shorter height in adulthood [P-113][5].
  • Aromatase Inhibitors: Medications like letrozole are a specialist-selected option sometimes used to block the production of estrogen. However, responses vary, and it is often used off-label. Letrozole has been used to successfully slow down skeletal maturation and reduce bleeding episodes in some cases, though alternative approaches may be selected based on age, bone age, and cyst activity [5][6].
  • Central Puberty: While standard “puberty blockers” (GnRH agonists) do not suppress the autonomous peripheral hormone source, they may become useful if recurrent peripheral sex-steroid exposure later triggers secondary “central” puberty [7].
  • Monitoring: Your care team will likely track “bone age” using hand X-rays and use pelvic ultrasounds to monitor ovarian cysts [8][9]. Adults should also discuss fertility, contraception, and pregnancy planning with a specialist.

Growth Hormone (GH) Excess: A Silent Risk

An estimated 10–15% of people with MAS produce too much growth hormone. This is often “silent” because many MAS patients are already tall due to early puberty, making the excess growth hard to spot [10][11].

  • Craniofacial Impact: This is the most critical area of GH management. Uncontrolled growth hormone is associated with more severe or progressive fibrous dysplasia (FD), especially in the skull and face. It is linked to faster bone regrowth after surgery, facial asymmetry, and a higher risk of vision or hearing loss [11][12].
  • Screening: Experts recommend checking IGF-1 levels (a screening marker interpreted for age and pubertal stage) regularly. If levels are high, an oral glucose tolerance test (OGTT) is used to confirm the diagnosis [10].
  • Treatment: Medications such as lanreotide or octreotide (somatostatin analogs) are often used to bring GH levels down. In some cases, drugs like pegvisomant are added to block the hormone’s effects as part of individualized endocrine care [11][13].

Hyperthyroidism: The Overactive Thyroid

The thyroid gland in MAS can develop nodules that produce too much thyroid hormone (hyperthyroidism) [14].

  • Symptoms: This can cause a racing heart, anxiety, tremors, or heat intolerance [15].
  • Management: Doctors typically use antithyroid medications like methimazole or carbimazole. Because MAS-related hyperthyroidism rarely goes away on its own, some patients eventually choose an individualized option like surgery (total thyroidectomy), which has operative risks and requires lifelong thyroid-hormone replacement [1][16][17].
  • Surgical Safety: It is vital that thyroid levels are normal before any unrelated surgery (like an orthopedic procedure), as uncontrolled hyperthyroidism can lead to a dangerous “thyroid storm” during anesthesia [15]. (Patients on methimazole/carbimazole should contact their doctor urgently if they develop a sudden fever or sore throat to check white blood cell counts).

Phosphate Wasting: The Bone’s Building Blocks

Some fibrous dysplasia lesions produce a hormone called FGF23. This hormone tells the kidneys to inappropriately flush out phosphate, an essential building block for hard bone. If you excrete too much phosphate, your bones become soft (a condition called osteomalacia), which leads to more pain and more frequent fractures [2][18].

  • Conventional Therapy: The standard treatment is a combination of oral phosphate supplements and active Vitamin D (calcitriol or alfacalcidol). This must be taken several times a day to keep levels steady [2][19].
  • Burosumab: This is a newer, injectable medication that blocks FGF23. It is currently an off-label, investigational option for MAS patients, though early studies and case reports show it may help normalize phosphate levels and improve bone pain for those who don’t respond to standard pills [20][21][22].
  • Side Effects: Supplements must be carefully balanced to avoid kidney stones or “secondary hyperparathyroidism,” so frequent fasting serum phosphate and renal phosphate handling blood/urine tests are necessary [2][23].

Common questions in this guide

What hormone problems can McCune-Albright syndrome cause?
McCune-Albright syndrome can cause early puberty, excess growth hormone, an overactive thyroid, and phosphate wasting. These problems may occur together or at different times, so the care team checks which conditions are active and adjusts monitoring and treatment.
How is early puberty managed in McCune-Albright syndrome?
Treatment may use letrozole to reduce estrogen effects, control bleeding, and slow the rapid maturation of bones, but the response varies and use may be off-label. Doctors may track bone age with hand X-rays and monitor ovarian cysts with ultrasound; standard puberty blockers are generally useful only if central puberty develops later.
How is growth hormone excess found and treated in MAS?
Growth hormone excess can be difficult to notice, so doctors often screen with an IGF-1 blood test and use an oral glucose tolerance test if the result is high. Treatment may include lanreotide or octreotide, with pegvisomant added in some individualized plans to reduce the hormone's effects.
What happens if McCune-Albright syndrome causes hyperthyroidism?
An overactive thyroid can cause a racing heart, anxiety, tremors, and feeling unusually hot. Doctors may use methimazole or carbimazole, and some people eventually need thyroid removal followed by lifelong thyroid-hormone replacement; thyroid levels should be controlled before planned surgery.
How is phosphate wasting treated in McCune-Albright syndrome?
Some fibrous dysplasia lesions release FGF23, which makes the kidneys lose too much phosphate and can soften bones. Treatment usually combines oral phosphate with active vitamin D, while burosumab is an off-label or investigational option for selected people who do not respond to standard treatment.
What monitoring is needed when taking phosphate and vitamin D?
Regular blood and urine testing checks phosphate levels, kidney phosphate handling, and signs of secondary hyperparathyroidism. Doses must be balanced because too much supplementation can increase the risk of kidney stones or other mineral complications.

Questions For You

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Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Which of my (or my child's) endocrinopathies are currently 'active' versus 'stable', and how does that affect our screening schedule?
  2. 2.Is our current goal with letrozole to stop bleeding episodes, or is it primarily to slow down 'bone age' advancement?
  3. 3.Since growth hormone (GH) excess can be 'quiet,' how often should we be checking IGF-1 levels, especially before any planned facial or skull surgeries?
  4. 4.If we are managing phosphate wasting, what are the specific signs of 'secondary hyperparathyroidism' we should be monitoring in the blood work?
  5. 5.Can you review the latest research on burosumab for MAS—is it an option for us if oral phosphate supplements are causing stomach issues?

References

References (23)
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    Best practice management guidelines for fibrous dysplasia/McCune-Albright syndrome: a consensus statement from the FD/MAS international consortium.

    Javaid MK, Boyce A, Appelman-Dijkstra N, et al.

    Orphanet journal of rare diseases 2019; (14(1)):139 doi:10.1186/s13023-019-1102-9.

    PMID: 31196103
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    Phosphatonins: From Discovery to Therapeutics.

    Kritmetapak K, Kumar R

    Endocrine practice : official journal of the American College of Endocrinology and the American Association of Clinical Endocrinologists 2023; (29(1)):69-79 doi:10.1016/j.eprac.2022.09.007.

    PMID: 36210014
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    Peripheral precocious puberty in girls with McCune-Albright syndrome: a case series.

    Faria AG, Montenegro LR, Jorge AAL, et al.

    Archives of endocrinology and metabolism 2025; (69(2)):e240459 doi:10.20945/2359-4292-2024-0459.

    PMID: 40366083
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    McCune-Albright syndrome, a rare form of precocious puberty: Diagnosis, treatment, and follow-up.

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    Archivos argentinos de pediatria 2021; (119(5)):e420-e427 doi:10.5546/aap.2021.eng.e420.

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    Long-term outcomes of letrozole treatment for precocious puberty in girls with McCune-Albright syndrome.

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    European journal of endocrinology 2016; (175(5)):477-483 doi:10.1530/EJE-16-0526.

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    Management of precocious puberty in girls with McCune-Albright syndrome using letrozole.

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    Etiology and therapeutic outcomes of children with gonadotropin-independent precocious puberty.

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    [Efficacy and safety of letrozole in treatment of McCune-Albright syndrome girls with peripheral precocious puberty].

    Xu , Lu W, Wang X, et al.

    Zhejiang da xue xue bao. Yi xue ban = Journal of Zhejiang University. Medical sciences 2020; (49(3)):291-296 doi:10.3785/j.issn.1008-9292.2020.05.02.

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    Treatment of Peripheral Precocious Puberty.

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    Autonomous growth hormone secretion due to McCune Albright syndrome in paediatric age group: an ominous triad.

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    Growth hormone-Insulin-like growth factor 1 axis hyperactivity on bone fibrous dysplasia in McCune-Albright Syndrome.

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    Surgical Management of Polyostotic Craniofacial Fibrous Dysplasia: Long-Term Outcomes and Predictors for Postoperative Regrowth.

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    Pasireotide: potential treatment option for McCune-Albright-associated acromegaly.

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    GNAS mutated thyroid carcinoma in a patient with Mc Cune Albright syndrome.

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    Postoperative thyroid crisis in an 11-year old male with McCune-Albright syndrome and atypical triiodothyronine hyperthyroidism: A case report.

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    Case report: Surgical treatment of McCune-Albright syndrome with hyperthyroidism and retrosternal goiter: A case report and literature review.

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    Hyperthyroidism in McCune-Albright Syndrome - a case report.

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    Scoliosis in Fibrous Dysplasia/McCune-Albright Syndrome: Factors Associated With Curve Progression and Effects of Bisphosphonates.

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This page explains endocrine problems and treatment options in McCune-Albright syndrome for informational purposes only and does not constitute medical advice. Your endocrinologist should tailor testing and treatment to your or your child's hormone levels, age, and overall health.