title: Thymic hyperplasia in a child treated with growth hormone.
abstract: OBJECTIVE
  To report a case of thymic hyperplasia diagnosed three months after initiation of recombinant human growth hormone (GH) for the treatment of GH deficiency.
  
  
  METHODS
  Retrospective chart review was conducted to evaluate the temporal relationship between treatment with GH and thymic enlargement in a 7-year-old girl who had a history of embryonal rhabdomyosarcoma of the nasopharynx diagnosed at the age of 3 years.
  
  
  RESULTS
  The diagnosis of GH deficiency was made based on clinical and auxological criteria, an insufficient response to clonidine-arginine stimulation testing (peak GH level of 4.8 microg/L) and low insulin-like growth factor 1 (IGF-1) level (30 ng/mL, -2.7 SD). The patient was started on GH at a dose of 0.3mg/kg/week. At the initiation of treatment with GH, the baseline growth velocity was 0.8 cm/year (-6.0 SD) and height was 112.5 cm (-1.7 SD). After three months of treatment with GH, her height increased by 4.2 cm (from -1.7 to -1.2 SD), and the IGF-1 level from -2.7 SD to -1.1 SD. A chest CT performed at that time for recurrence surveillance showed 89% increase in thymic volume relative to previous scan before treatment with growth hormone. A thoracoscopic biopsy of the thymus was performed and revealed hyperplasia with normal thymic architecture without evidence of malignancy.
  
  
  CONCLUSIONS
  The timing of the development of thymic hyperplasia, along with data from in vitro and in vivo animal studies showing that GH and IGF-1 can directly stimulate growth of the thymus, suggests that GH contributed to the development of thymic hyperplasia in this patient.
authors.affiliation: Department of Pediatrics, University of Minnesota, Minneapolis, MN 55455-0356, USA.
authors.forename: Lynda
authors.initials: L
authors.lastname: Polgreen
authors.forename: Marie
authors.initials: M
authors.lastname: Steiner
authors.forename: Charles A
authors.initials: CA
authors.lastname: Dietz
authors.forename: J Carlos
authors.initials: JC
authors.lastname: Manivel
authors.forename: Anna
authors.initials: A
authors.lastname: Petryk
mesh_terms: D002648:Child; D004393:Dwarfism, Pituitary / Q000188:drug therapy; D005260:Female; D013006:Growth Hormone / Q000009:adverse effects* / Q000627:therapeutic use; D006801:Humans; D013952:Thymus Hyperplasia / Q000139:chemically induced* / Q000000981:diagnostic imaging / Q000473:pathology; D014057:Tomography, X-Ray Computed
chemical_list: D013006:Growth Hormone