Sheep beta-LPH is a hypophyseal lipolytic hormone with defined chemical structure which has been shown to be hypocalcemic when injected into rabbits. The thyroid gland seems to be essential for production of this hypocalcemic effect. Beta-LPH may be a stimulating hormone for calcitonin-secreting cells. It has no effect on plasma magnesium, cholesterol, triglycerides, and glucose, at least in short-term experiments. When intact epididymal fat pads are used for the determination of the LPH lipolytic effect in vitro, a lower minimum effective dose is found than when small pieces are used.