A compound of formula wherein: R 1 represents hydrogen, halogen, cyano, trifluoromethyl, nitro, -OR a, SR a, SOR a, -SO 2 R a, - SO 2 NR a R b, -NR a R b, -NR a COR b, -NR a CO 2 R b, -COR a, -CO 2 R a, -CONR a R b, or a hydrocarbon group comprising a straight chain, branched or cyclic group each containing up to 18 carbon atoms, or a heterocyclic group containing up to 18 carbon atoms and at least one heteroatom; R 2 represents, independently at each occurrence, hydrogen, halogen, cyano, trifluoromethyl, nitro, -OR a, SR a; SOR a; -SO 2 R a; -SO 2 NR a R b; -NR a R b; -NR a COR b, -NR a CO 2 R b. -COR a; -CO 2 R a; - CONR a R b, or a hydrocarbon group comprising a straight chain, branched or cyclic group each containing up to 18 carbon atoms, or a heterocyclic group containing up to 18 carbon atoms and at least one heteroatom; R 3 represents a hydrocarbon group comprising a straight chained, branched or cyclic group each containing up to 18 carbon atoms, substituted by at least one moiety including a -CO 2 R a substituent, wherein R 3 is represented by the following Formula; -[CR c R d] q -[R c R e C ---- CR c R e] r -[CR c R d] s -CO 2 R a where the unattached bond represents the point of attachment of the structural fragment of Formula to the rest of the compound of Formula; R c, R d and R e are independently selected from hydrogen or C 1-6 alkyl (which can be straight chained or branched); q is 1, 2, 3 or 4; r and s are independently selected from 0, 1, 2, 3 or 4; ------ represents a double bond, and R e is not present above formula; optionally wherein the structural fragment of Formula is selected from: -CH 2 CH=C(CH 3)(CH 2) 2 CO 2 H; and -CH 2 CH=C(CH 3)CO 2 H. wherein R a and R b independently represent, at each occurrence, hydrogen, or a hydrocarbon group comprising a straight chained, branched or cyclic group each containing up to 18 carbon atoms, or a heterocyclic group containing up to 18 carbon atoms and at least one heteroatom; and; or a pharmaceutically acceptable solvate or, more particularly, salt thereof; for use in the treatment of osteoporosis and/or osteopenia. R 1 represents hydrogen, halogen, cyano, trifluoromethyl, nitro, -OR a, SR a, SOR a, -SO 2 R a, - SO 2 NR a R b, -NR a R b, -NR a COR b, -NR a CO 2 R b, -COR a, -CO 2 R a, -CONR a R b, or a hydrocarbon group comprising a straight chain, branched or cyclic group each containing up to 18 carbon atoms, or a heterocyclic group containing up to 18 carbon atoms and at least one heteroatom; R 2 represents, independently at each occurrence, hydrogen, halogen, cyano, trifluoromethyl, nitro, -OR a, SR a; SOR a; -SO 2 R a; -SO 2 NR a R b; -NR a R b; -NR a COR b, -NR a CO 2 R b. -COR a; -CO 2 R a; - CONR a R b, or a hydrocarbon group comprising a straight chain, branched or cyclic group each containing up to 18 carbon atoms, or a heterocyclic group containing up to 18 carbon atoms and at least one heteroatom; R 3 represents a hydrocarbon group comprising a straight chained, branched or cyclic group each containing up to 18 carbon atoms, substituted by at least one moiety including a -CO 2 R a substituent, wherein R 3 is represented by the following Formula; -[CR c R d] q -[R c R e C ---- CR c R e] r -[CR c R d] s -CO 2 R a R c, R d and R e are independently selected from hydrogen or C 1-6 alkyl (which can be straight chained or branched); q is 1, 2, 3 or 4; r and s are independently selected from 0, 1, 2, 3 or 4; ------ represents a double bond, and R e is not present above formula; optionally wherein the structural fragment of Formula is selected from: -CH 2 CH=C(CH 3)(CH 2) 2 CO 2 H; and -CH 2 CH=C(CH 3)CO 2 H.