High third generation/second generation PTH ratio in a patient with parathyroid carcinoma: clinical utility of third generation/second generation PTH ratio in patients with primary hyperparathyroidism.
BACKGROUND
Primary hyperparathyroidism (PHP) is caused by parathyroid adenomas or hyperplasia, and occasionally by parathyroid carcinoma. Recently a high third generation/second generation PTH ratio has been observed in some patients with parathyroid carcinoma.


METHODS
We report the case of a 60-year old woman who was presented a fourth episode of PTH-related hypercalcaemia due to a parathyroid carcinoma. Serum PTH levels were measured using a second generation assay and a third generation assay before, 4 and 7 months after the fourth surgery. Then, PTH levels were measured in 294 osteoporotic normocalcaemic patients as well as in 30 consecutive PHP patients.


RESULTS
Before surgery of the patient with parathyroid carcinoma, second generation PTH was 229 pg/ml, third generation PTH was 675 pg/ml and third generation/second generation PTH ratio was 2.95. Four and 7 months after surgery the third generation/second generation PTH ratio was 0.70 and 0.66, respectively. All osteoporotic patients had a normal third generation/second generation PTH ratio (0.585 +/- 0.118) whereas only one patient (3.3%) with PHP had a third generation/second generation PTH ratio > 1 (1.54).


CONCLUSIONS
A high third generation/second generation PTH ratio could be observed in patients with parathyroid carcinoma, is uncommon in benign PHP and is absent in osteoporotic patients without PHP. Therefore, PTH level can be measured using second and third generation assays in some PHP patients, and a specific surgical protocol for possible parathyroid carcinoma could be discussed in patients with a high third generation/second generation PTH ratio.
Caron
Philippe
P
Department of Endocrinology and Metabolic diseases, CHU Larrey, Toulouse, Cedex, France. caron.p@chu-toulouse.fr
Maiza
Jean Christophe
JC
Renaud
Claire
C
Cormier
Catherine
C
Barres
Béatrice Herbault
BH
Souberbielle
Jean Claude
JC
D000368:Aged; D002118:Calcium / Q000097:blood; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006801:Humans; D006934:Hypercalcemia / Q000097:blood; D049950:Hyperparathyroidism, Primary / Q000097:blood* / Q000601:surgery; D015592:Immunoradiometric Assay; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000097:blood; D010281:Parathyroid Hormone / Q000097:blood*; D010282:Parathyroid Neoplasms / Q000097:blood* / Q000601:surgery; D016105:Parathyroidectomy; D010446:Peptide Fragments / Q000097:blood
D010281:Parathyroid Hormone; D010446:Peptide Fragments; C414937:parathyroid hormone (7-84); D002118:Calcium