PURPOSE: To provide the subject side effect-free improver of high safety, useful for osteoporosis, hypercalcemia, alveolar bone resorption etc., containing a specific pyrazolopyrazine derivative.

CONSTITUTION: The objective improver containing an 1H-pyrazolo[3,4-b]pyrazine derivative of the formula [R1 is H, vinyl or CH2CH2R4 (R4 is OH, acetyloxy, succinyloxy or halogen); R2 and R3 are each H, halogen, (substituted) lower alkyl or lower alkoxy], e.g. 5,6-bis(p-chlorophenyl)-1H-pyrazolo[3,4b]pyrazine. The dose of this derivative is pref. 10-3000mg/day.