BACKGROUND Increased secretion of growth hormone leads to gigantism in children and acromegaly in adults; the genetic causes of gigantism and acromegaly are poorly understood. METHODS We performed clinical and genetic studies of samples obtained from 43 patients with gigantism and then sequenced an implicated gene in samples from 248 patients with acromegaly. RESULTS We observed microduplication on chromosome Xq26.3 in samples from 13 patients with gigantism; of these samples, 4 were obtained from members of two unrelated kindreds, and 9 were from patients with sporadic cases. All the patients had disease onset during early childhood. Of the patients with gigantism who did not carry an Xq26.3 microduplication, none presented before the age of 5 years. Genomic characterization of the Xq26.3 region suggests that the microduplications are generated during chromosome replication and that they contain four protein-coding genes. Only one of these genes, GPR101, which encodes a G-protein–coupled receptor, was overexpressed in patients’ pituitary lesions. We identified a recurrent GPR101 mutation (p.E308D) in 11 of 248 patients with acromegaly, with the mutation found mostly in tumors. When the mutation was transfected into rat GH3 cells, it led to increased release of growth hormone and proliferation of growth hormone–producing cells. CONCLUSIONS We describe a pediatric disorder (which we have termed X-linked acrogigantism [X-LAG]) that is caused by an Xq26.3 genomic duplication and is characterized by early-onset gigantism resulting from an excess of growth hormone. Duplication of GPR101 probably causes X-LAG. We also found a recurrent mutation in GPR101 in some adults with acromegaly. (Funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development and others.)

X-linked acro-gigantism (X-LAG) is a new syndrome of pituitary gigantism, caused by microduplications on chromosome Xq26.3, encompassing the gene GPR101, which is highly upregulated in pituitary tumors. We conducted this study to explore the clinical, radiological and hormonal phenotype and responses to therapy in patients with X-LAG syndrome. The study included 18 patients (13 sporadic) with X-LAG and a microduplication in chromosome Xq26.3. All sporadic cases had unique duplications and the inheritance pattern in 2 families was dominant with all Xq26.3 duplication carriers being affected. Patients began to grow rapidly as early as 2–3 months of age (median 12 months). At diagnosis (median delay 27 months), patients had a median height and weight SDS score of >+3.9 SDS. Apart from the increased overall body size, the children had acromegalic symptoms including acral enlargement and facial coarsening. More than a third of cases had increased appetite. Patients had marked hypersecretion of GH/IGF-1 and prolactin, usually due to a pituitary macroadenoma or hyperplasia. Primary neurosurgical control was achieved with extensive anterior pituitary resection but postoperative hypopituitarism was frequent. Control with somatostatin analogs was not readily achieved despite moderate to high somatostatin receptor subtype-2 expression in tumor tissue. Postoperative adjuvant pegvisomant achieved control of IGF-1 all 5 cases in which it was employed. X-LAG is a new infant-onset gigantism syndrome that has a severe clinical phenotype leading to challenging disease management.

The materials of the National Consensus reflect the modern domestic and international experience on this issue. Before conducting a specialized endocrinological examination of a short child, all other causes of short stature should be excluded: severe somatic diseases in a state of decompensation that can affect growth velocity, congenital systemic skeletal diseases, syndromic short stature (all girls with growth retardation require a mandatory study of karyotype, depending on the presence or absence of phenotypic signs of Turner syndrome), endocrine diseases in decompensation. A specialized examination of the state of GH-IGF-I axis is carried out when the proportionally folded child has pronounced short stature: if the child’s height is < –2.0 SDS, if the difference between the child’s height SDS and child’s midparental height SDS exceeds 1.5 SDS and/or a low growth velocity. The consensus reflects clear criteria for the diagnosis of GH-deficiency, central hypothyroidism, central hypocorticosolism, central hypogonadism, diabetes insipidus, hypoprolactinemia, and also the criteria for their compensation. The dose of somatropin with GH-deficiency in children and adolescents is 0.025–0.033 mg/kg/day. With total somatotropic insufficiency, especially in young children, it is advisable to start therapy with somatropin from lower doses: 25–50% of the substitution, gradually increasing it within 3–6 months to optimal. In children with a growth deficit when entering puberty, the dose may be increased to 0.045–0.05 mg/kg/day. With the development of side effects, the dose of somatropin can be reduced (by 30–50%), or temporarily canceled (depending on the severity of the clinical picture) until the complete disappearance of undesirable symptoms. With swelling of the optic nerve, treatment is temporarily stopped until the picture of the fundus of the eye fully normalizes. If therapy has been temporarily discontinued, treatment is resumed in smaller doses (50% of the initial) with a gradual (within 1–3 months) return to the optimum. GH treatment at pediatric doses not continue beyond attainment of a growth velocity below 2–2.5 cm/year, closure of the epiphyseal growth zones, or earlier, when: the achievement of genetically predicted height, but not more than 170 cm in girls, 180 cm in boys, the patient’s desire and his parents / legal representatives satisfied with the achieved result of the final height. Re-evaluation of the somatotropic axis is carried out after reaching the adult height, after 1–3 months GH therapy will be discontinued. Patients with isolated GH-deficiency or patients with 1 (besides GH) pituitary hormone deficiencies in the presence of a normal IGF-1 level (against the background of somatropin withdrawal) and not having molecular genetic confirmation of the diagnosis need re- evaluation. Patients with two or more (besides GH) pituitary hormone deficiencies, acquired hypothalamic-pituitary lesions due to operations on the pituitary and irradiation of the hypothalamic-pituitary area (if the IGF-1 level is low against somatropin withdrawal), specific pituitary/ hypothalamic structural defect on MRI, gene defects of the GH-IGF-I system do not need re- evaluation. If GH deficiency is confirmed, treatment with somatropin is resumed at metabolic doses of 0.01—0.003 mg/kg/day under the control of the IGF-I level in the blood (measurement 1 time in 6 months), the indicator should not exceed the upper limit of the reference value for the corresponding age and floor.