On its own, a lack of progesterone probably doesn't cause the attacks. If it did, men would have them constantly. If you take Valium for a while and then abruptly stop, you feel terrible. What Le Melledo is looking for is a chemical link between progesterone levels and the stress response process - how quickly people react to danger, real or imagined. And the problem goes beyond simple jitters.
Panic attacks place people at a higher risk of sudden cardiac arrest.
Fear is not good for your health, sometimes. He's injected himself with the stuff twice. He won't do it a third time. It impacts the fear centre of the brain. The effect is an immediate feeling of intense fear, followed by palpitations and sweating.