Lanreotide therapy in a 5-year-old Female with Growth Hormone Excess Secondary to McCune Albright Syndrome

Objectives McCune Albright syndrome (MAS) is a heterogenous genetic syndrome that results from somatic activating mutations in GNAS, resulting in hyperfunctioning endocrinopathies and bone fibrous dysplasia. Growth Hormone (GH) excess is seen in up to 30% of the cases and more commonly identified in adulthood (Salenave S et al; 2014). Currently, there is limited scientific evidence of successful treatment of GH excess in children. With this case report, we share our experience with the use of Lanreotide in a case of pediatric GH excess secondary to MAS. Methods A 5-year-old female presented with tachycardia, linear growth acceleration, and goiter. Work up studies identified elevated Free T4 2.1 ng/dL (0.9-1.4), suppressed TSH <0.01, elevated IGF-1 548 ng/mL (z-score +3.2); pre-pubertal gonadotropins and estradiol, and negative thyroid antibodies. On physical exam, the patient had tall stature, asymmetrical goiter, but no café-au-lait macules or signs of precocious puberty. Thyroid uptake scan and ultrasound were normal. She was initiated on atenolol and methimazole for primary hyperthyroidism. A CT scan of the neck was obtained to evaluate the neck mass and it incidentally revealed fibrous dysplasia in multiple cranial bones. GH excess was then suspected in the setting of probable MAS. Random GH was elevated at 16.7 ng/mL (0.1- 6.2). Brain MRI described polyostotic fibrous dysplasia and mass effect of dysplastic sphenoid bone on the pituitary, with no suggestion of adenoma. Patient was initiated on Lanreotide for treatment of GH excess. Results Lanreotide was started at 60 mg Q4 weeks SQ with normalization of IGF-1 to 223 ng/mL (z-score +1.3) (see Table 1 and Fig 1); and progressive improvement in growth velocity from 7.8cm/year to 1cm/year in the first 6 months of therapy. Lanreotide was then decreased to 60 mg Q6 weeks. Progressive improvement of hyperthyroidism allowed discontinuation of methimazole. Patient has tolerated treatment well without adverse events. Conclusions MAS is a heterogeneous syndrome and clinical suspicion aids prompt diagnosis and targeted treatment. Hyperthyroidism, precocious puberty, and GH excess can all manifest with growth acceleration. In the appropriate clinical setting, biochemical screening of hormone excess contributes to early identification of hyperactive endocrinopathies in MAS that can present concurrently. This clinical case reflects the efficacy and safety of Lanreotide in the medical management of GH excess in a pediatric patient with MAS. .