A biologically active parathyroid hormone-like substance secreted by an adenosquamous carcinoma of the transverse colon.

Recently, controversy has emerged as to whether paraneoplastic hypercalcemia in nonparathyroid tumors is due to ectopic production of a parathyroid hormone (PTH)-like substance. A sensitive DNA hybridization technique was unable to reveal PTH mRNA in a collection of such tumors. However, there is growing evidence that squamous differentiation of tumors favors the expression of PTH-like substances. We report the case of a 41-year-old woman with an adenosquamous carcinoma of colonic origin associated with severe hypercalcemia. The squamous component of liver metastases showed immunoreactivity with two different PTH antisera, suggesting the production of a PTH-like substance.