Evaluation of the parathyroid function in six patients with hypophosphatemic osteomalacia, including a case of tertiary hyperparathyroidism developing during combined oral phosphate and vitamin D therapy.
OBJECTIVE
To describe a case of tertiary hyperparathyroidism after long-term phosphate and vitamin D therapy and the retrospective evaluation of parathyroid function in 6 patients with hypophosphatemic osteomalaica.


METHODS
We evaluated the parathyroid function by measuring iPTH before and during treatment and divided the patients into normal and elevated serum iPTH groups.


RESULTS
In the normal serum iPTH group, the 4 patients were all males, whereas the 2 patients in the elevated serum iPTH group were females. Clinical characteristics and biochemical results showed no differences between the two groups. One of the women with an elevated iPTH level (224 pg/ml) had a normal serum calcium level and no evidence of increasing parathyroid uptake by (99m)Tc-MIBI scan 52 months after treatment. The other woman also had an elevated iPTH level (483 pg/ml) and a normal serum calcium level 56 months after treatment. However, in this latter case both her iPTH (1,447 pg/ml) and serum calcium (11.3 mg/dl) levels were elevated 113 months after treatment, when a (99m)Tc-MIBI scan showed increased uptake in all four parathyroid glands during early and delayed phases of the scan. Parathyroidectomy was performed after the diagnosis of tertiary hyperparathyroidism was made, and the histological findings showed adenomatous hyperplasia.


CONCLUSIONS
Our findings indicate that even with vitamin D therapy, long-term phosphate therapy may lead to the development of secondary or tertiary hyperparathyroidism in hypophosphatemic osteomalacia and, therefore, suggest that it is important to carefully monitor the parathyroid function during therapy in those with hypophosphatemic osteomalacia.
Jeon
Hyun Jeong
HJ
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Kwon
Seong Hee
SH
Kim
Sang Wan
SW
Shin
Chan Soo
CS
Park
Kyung Soo
KS
Kim
Seong Yeon
SY
Cho
Bo Yeon
BY
Lee
Hong Kyu
HK
D000328:Adult; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D006961:Hyperparathyroidism / Q000097:blood / Q000139:chemically induced*; D017674:Hypophosphatemia / Q000150:complications*; D008297:Male; D008875:Middle Aged; D010018:Osteomalacia / Q000209:etiology* / Q000503:physiopathology*; D010280:Parathyroid Glands / Q000503:physiopathology*; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000009:adverse effects*; D014807:Vitamin D / Q000627:therapeutic use*
D010281:Parathyroid Hormone; D010710:Phosphates; D014807:Vitamin D