Both mine had a growth spurt at 4 months.
With DS1, it coincided with just about every sign there is to say he was ready to wean. He was actually drooling when he saw food, and trying to snatch it off our plates. I felt almost cruel letting him be in a room where adults were eating. He started baby rice, and slept through again from that night.
DS2, breastfed, clearly not remotely interested in food at that point, tried to increase the breastfeeds, but was suffering from thyroid problems and it nearly floored me, so I introduced two formula feeds. Still didn't help with the night feeds, and he didn't sleep through until I weaned at 5 months.
If your baby's clearly ready to wean, then wean. if not, and you can stand the increased BFs then do that. If it's too much for you, then a bottle of formula.
(Better mention that, once I'd introduced formula, the breastfeeds carried on for another two months, but at sic months, he was refusing at some feeds, and trying to grab my changing bag where I kept the bottles!)