Parathyroid hormone concentration gradients across the human bone marrow

Parathyroid hormone (PTH) concentrations were compared in blood drawn from the bone marrow and antecubital vein of patients undergoing marrow biopsy for suspected hematological neoplasia. Radioimmunological analysis revealed that the bone marrow blood had a higher PTH content than blood from the peripheral circulation. Thyroid hormone-binding globulin was not distributed asymmetrically, showing that the gradient is PTH specific. The intact PTH content of marrow blood was 65% greater than that in the venous system, whereas carboxyl regional PTH levels showed a 34% gradient in favor of the marrow. Although the majority of patients were found to have hematological malignancies, there was no discernable influence of tumor on the PTH gradients. The physiological implications and possible origins of the asymmetrical PTH distribution are discussed.