PTH and parathyroid gland carcinoma: Perhaps because of these dual pathophysiologic mechanisms, serum levels of PTH do not correlate particularly well with the size of the adenoma in typical cases of PHPT(72, 73) and even when such a correlation has been reported, gland size has been found to vary widely with a given level of circulating PTH, especially when the PTH value is mildly to moderately elevated.(74) Extreme elevations in PTH do, however, raise the specter of parathyroid carcinoma.