^{Skeleton growth is dependent on the proper functioning of systemic or circulating hormones that respond to changes in blood calcium and phosphorus. The regulating hormones take calcium and phosphorus out of bone to serve vital functions in other systems of the body if the minerals are lacking. Growth hormone is also an important regulator of skeletal growth and acts by stimulating the production of insulin-like growth factor-1 (IGF-1 – see Sept/Oct 1999 HIV ReSource Review). IGF-1 is made in the liver and locally in other tissues, particularly in bone, also under the control of growth hormone. Growth hormone may also directly affect the bone. (18) Although the growth hormone/IGF-1 system stimulates both the bone-resorbing and bone-forming cells, the dominant effect is on bone formation resulting in increased bone mass.}

^{Insulin is also important for bone growth, which makes it important for HIV-positive people with glucose abnormalities to learn about bone disorders. The response to other factors that stimulate bone growth is impaired in individuals with insulin deficiency. (5) Leptin (review the March/April 2003 HIV Nutrition Update), also has effects on bone.}

^{There are several bone builders besides calcium, vitamin D, vitamin C, and vitamin K. These include the minerals copper, zinc, and potassium, which may help the body hold onto calcium; boron that may increase the absorption of calcium, magnesium, phosphorus, and manganese. (19, 20) Individuals need more vitamin D as they get older (Figure 1). (1, 5) Calcium and vitamin D recommendations may not be appropriate for people in all countries due to different dietary patterns and environmental factors. Vitamin D researchers such as Dr. Michael Holick believe the DRI for Vitamin D for people with minimal sun exposure should be 1,000 IU daily. (21)}