Not precisely. Most of the energy of a thermonuclear bomb comes from fission, the fusion reaction mostly serves as a booster for neutron flux, escalating the fission reaction further than in a pure fission weapon. Even more so when the enclosing capsule (The tamper) is made of U238 instead of lead, as the high neutron flux leads to fission in the tamper (The Tsar Bomb would have had a yield of 100MT instead of 50MT had it's tamper not been replaced by lead, an intentional restriction).

A proper hydrogen bomb would be purely fusion.