Interactions between PTH and adiposity: appetizing possibilities.

ABSTRACT

Although parathyroid hormone (PTH) is best known for its role as a regulator of skeletal remodelling and calcium homeostasis, more recent evidence supports a role for it in energy metabolism and other non-classical targets. In this report, we summarize evidence for an effect of PTH on adipocytes. This review is based upon all peer-reviewed papers, published in the English language with PubMed as the primary search engine. Recent preclinical studies have documented an effect of PTH to stimulate lipolysis in both adipocytes and liver cells and to cause browning of adipocytes. PTH also reduces bone marrow adiposity and hepatic steatosis. Although clinical studies are limited, disease models of PTH excess and PTH deficiency lend support to these preclinical findings. This review supports the concept of PTH as a polyfunctional hormone that influences energy metabolism as well as bone metabolism.

Parathyroid hormone controls skeletal and circulating calcium levels. Its secretion by the four parathyroid glands is regulated primarily by the concentration of the ionized calcium level. The other major target organ for parathyroid hormone is the kidney where it conserves filtered calcium by effects on the renal tubules. While bone and the kidney are indisputably the main target organs for PTH, recent studies are pointing to systems and organs that can be shown also to respond to PTH. One of these systems that PTH appears to target is fat cells, an important storehouse for energy. This review summarizes what is known about PTH's effects to stimulate the production of energy from fat cells when present in excess or to reduce the production of energy when deficient.