  From Newtonian potential-density pairs we construct three-dimensional
axisymmetric relativistic sources for a Majumdar-Papapetrou type conformastatic
spacetime. As simple examples, we build two family of relativistic thick disks
from of the first two Miyamoto-Nagai potential-density pairs used in Newtonian
gravity to model flat galaxies, and a three-component relativistic model of
galaxy (bulge, disk and dark matter halo). We study the equatorial circular
motion of test particles around such structures. Also the stability of the
orbits is analyzed for radial perturbation using an extension of the Rayleigh
criterion. In all examples, the relativistic effects are analyzed and compared
with the Newtonian approximation. The models considered satisfying all the
energy conditions.
