PTH and vitamin D deficiency: MEN1 PHPT patients on average had vitamin D insufficiency (less than 30.0 ng/mL), while sPHPT patients on average had normal levels of vitamin D. All MEN1 PHPT and sPHPT patients with marked vitamin D insufficiency (less than 20.0 ng/mL) or deficiency (less than 10.0 ng/mL) were supplemented with this hormone, according to guidelines, to help control PTH oversecretion [14].