Poll - What side-effects could the serum have?

The focus of the story could be to explore the serum's side-effects, and overcoming them.
Although, I believe it's fair to think of them separately from the other story idea as some of the most minor ones could be explored if Option 2 won.

For example, the strength gained from the serum could cause mood swings, loss of inhibitions, violent tendencies? Maybe the serum's user develops a split-personality when enhanced.

Maybe the serum's user could experience changes in brain chemistry. Think of a 'Jekyll & Hyde' situation where the user temporarily becomes their opposite. The shy girl becomes dominant, the mean girl becomes loving.
With that, the serum could also cause short-term amnesia, or black-outs.

The serum could possibly cause subtle mutations, such as fangs, pointy nails and ears? Those effects could become more pronounced with increased exposure to the serum? Maybe it could depend on the serum's composition, if it's plant-based, animal-based, alien-based, etc?

Maybe like DC's Bane, the eye-color could change, and the user's veins could glow during the muscle growth?

Or the serum could perhaps give powers, like telepathy or telekinesis. Why not flight?!

Could the serum cause addiction?

Maybe the serum provides little growth on its own, but instead turns the user into a stamina-vampire who can somehow drain muscles from others?

Perhaps the serum causes some girls to lactate or squirt more, and their fluids have serum-like properties? This could also apply to the blood!

Maybe the growth can be turned on or off by strong emotions like the Hulk? Not just anger, but maybe love or sexual excitement?
Or the growth could be triggered by physical trauma/kinetic energy (ie being struck / shot at).

The serum could also give some very positive enhancements. For example, increased healing, perfect sight, increased intelligence, bullet-proof skin, inhuman agility?

On the flip-side, maybe the serum could be unstable and cause random growth-spurts or uneven growth?

There could be some drawbacks when the serum wears off. Extreme fatigue, muscular paralysis or hunger could make sense, to recover from the growth.

Maybe the serum is based on animal/human DNA, and it could trigger some genetic-memories. Think "Assassin's Creed", but when it was still good.

Maybe the serum is more than just a liquid, maybe it's sentient, like nano-tech or a symbiote, and it can communicate with the user and provide enhancements when asked, or it could take them away if taken for granted...
Maybe it also has it own wants and needs.

MULTIPLE CHOICE POLL: