title: A case of primary hyperparathyroidism due to ectopic parathyroid adenoma in the thymus, accompanied with vitamin D deficiency.
abstract: BACKGROUND
  Primary hyperparathyroidism (PHPT) caused by ectopic parathyroid adenoma (EPA) is not rare, whereas the concurrence of PHPT and vitamin D deficiency (VDD) in youth is uncommon. We reported a case of PHPT with EPA in the thymus, accompanied by a very low level of 25-hydroxyvitamin D.
  
  
  METHODS
  A 20-year-old man suffered from bilateral hip fractures under slight force or no force. Biochemical findings were consistent with PHPT and VDD. Examination results showed severe osteoporosis; both technetium-99m-sestamibi scintigraphy and computed tomography showed an abnormal nodule in the mediastinum, which was resected with a thoracoscope and confirmed pathologically as an EPA in the thymus. Hypocalcemia due to hungry bone syndrome (HBS) occurred after surgery and was resolved quickly with large-dose calcium and alfacalcidol supplementation.
  
  
  CONCLUSIONS
  PHPT is usually a sporadic disease, and VDD is unfortunately a common global problem. Negative family history and no concomitant illness seemed to rule out familiar hyperparathyroidism. VDD with no gastrointestinal symptom and nutritional anemia was caused by long-term inadequate sun exposure before the first fracture and a 2-year absence of sun exposure due to immobilization. Both PHPT and VDD contributed to severe osteoporosis, which could be exacerbated by not attaining his peak bone mass and by immobilization because of a fragile fracture with delayed healing. Large parathyroid adenoma, VDD, overt bone disease, and PTH resistance in the patient were related to postoperative hungry bone syndrome.
  
  
  CONCLUSIONS
  Any fracture in young adults that has not healed within 3 months should alert physicians to search for some factors or underlying diseases.
authors.affiliation: Department of Endocrinology, The Affiliated Sir Run Run Shaw Hospital, Zhejiang University, Hangzhou 310016, China.
authors.forename: Guoxing
authors.initials: G
authors.lastname: Wang
authors.forename: Haijuan
authors.initials: H
authors.lastname: Xiao
authors.forename: Zhenyang
authors.initials: Z
authors.lastname: Gu
authors.forename: Tongfeng
authors.initials: T
authors.lastname: Zhao
mesh_terms: D000328:Adult; D002828:Choristoma / Q000150:complications*; D006801:Humans; D049950:Hyperparathyroidism, Primary / Q000209:etiology*; D008297:Male; D010282:Parathyroid Neoplasms / Q000150:complications*; D013953:Thymus Neoplasms / Q000150:complications*; D014808:Vitamin D Deficiency / Q000150:complications*