Objective: To observe the efficacy and safety of Yigu capsule (YGC, a Chinese herbal compound preparation) in treating postmenopausal osteoporosis (PMO) and to explore its possible mechanism.

Methods: The clinical study was conducted adopting prospective, randomized, double blinded method for 6 months with placebo and positive controls. Two hundred and ten PMO patients with confirmed diagnosis were divided into the YGC group, the osteocalcin group and the placebo group, they were treated with YGC, osteocalcin capsule and placebo capsule, respectively. The symptoms, as new fracture and ostealgia, bone mineral density (BMD) of the 2nd to the 4th lumbar vertebrae (L24) and upper segment of femur, blood and urinary indexes for bone metabolism, sex hormone level and adverse reaction were observed.

Results: In the YGC group, the total effective rate was 95.50%, no new fracture occurred, which was significantly better than that in the other two groups (P < 0.05). The increase of BMD was 9.83% in L2-4, 4.09% in femoral neck, 4.60% in Wards triangle, 3.00% in greater trochanter, which were better than those in the placebo group (P < 0.05, P < 0.01). As compared with the placebo group, in the YGC group, levels of urinary oxyproline hydroxyproline/creatinine, urinary calcium/creatinine were lower, serum and bone alkaline phosphatase, osteocalcin, estradiol, and estradiol/testosterone were higher, but with no difference in level of testosterone. In the observation period, no abnormal findings in blood and urine routine examination as well as in liver and renal function were found. Mild, transient gastro-intestinal response occurred in individual patients but it didn't affect the treatment.

Conclusion: YGC could treat PMO effectively, it could obviously increase the BMD of lumbar vertebrae and hip, elevate the alleviating rate of ostealgia and incessant motion time, without new compressive fracture of vertebrae, and without any related adverse reaction. YGC could not only promote the formation, but also inhibit the absorption of bone, and increase the sex hormone level, therefore, it is a pure Chinese herbal compound preparation that worths further deep research and development.