title: Normocalcemic hyperparathyroidism in Vietnamese immigrants living in southern California.
abstract: OBJECTIVE
  To characterize the normocalcemic hyperparathyroidism in Vietnamese immigrants living in southern California.
  
  
  METHODS
  Of 14 Vietnamese patients with primary hyperparathyroidism who were observed between 1991 and 1996, 50% (7 patients; 2 men and 5 women) had normal and/or fluctuating levels of serum total calcium. When the serum calcium was corrected for the albumin, the "corrected" calcium was lower than the measured serum total calcium. Their mean age was 56.4 +/- 11.4 years. All patients had normal serum levels of albumin and serum phosphate.
  
  
  RESULTS
  Women were affected more often than men by a ratio of 5:2. The serum-ionized calcium as well as intact PTH were increased in all patients. Five patients underwent surgery with confirmation of parathyroid adenomas. Two patients refused surgery. They did not have osteitis fibrosa cystica by radiological examination. One patient had low plasma levels of 25-hydroxyvitamin D. Five of 7 normocalcemic patients (70%) were born in the month of December compared with 2 of seven hypercalcemic patients (30%).
  
  
  CONCLUSIONS
  The blood ionized calcium and intact parathyroid hormone are necessary for confirmation of normocalcemic hyperparathyroidism. Most of our normocalcemic hyperparathyroid patients (70%) were born in the month of December. We postulate that a combination of exposure to solar ultraviolet light during the formation of the fetal parathyroid glands and stimulation from low vitamin D levels in the wintertime may be related to the development of hyperparathyroidism. However, it is difficult to prove a definite correlation between normocalcemic hyperparathyroidism and their month of birth (December), especially when these observations were seen in a small group of patients.
authors.affiliation: Vietnamese American Medical Research Foundation, Westminster, California, USA.
authors.forename: K V
authors.initials: KV
authors.lastname: Luong
authors.forename: L T
authors.initials: LT
authors.lastname: Nguyen
mesh_terms: D000328:Adult; D000368:Aged; D002118:Calcium / Q000097:blood*; D002140:California / Q000453:epidemiology; D004641:Emigration and Immigration / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D006961:Hyperparathyroidism / Q000097:blood* / Q000453:epidemiology / Q000209:etiology; D008297:Male; D008875:Middle Aged; D012621:Seasons; D012709:Serum Albumin / Q000378:metabolism; D012737:Sex Factors; D014744:Vietnam / Q000208:ethnology
chemical_list: D012709:Serum Albumin; D002118:Calcium