You will have to reduce the resolution to 1920 x 1080. In Lightroom preferences it's possible to adjust font sizes a little. But that is the only control you have.
Actually Lightroom 5.7 can handle 3840x2160 resolution. As I was suspecting problem was with Windows 7. I found the right settings finally. It is where screen resolution can be set. Underneath there is a link "Make text and other items bigger or smaller". This is where things can be scaled. What confused me is that my laptop automatically switched to 200% after second start up and that Photoshop for example was working with the highest resolution available despite that scaling set for 200%. Anyway, thank you for answering my question.
Please go to edit>preferences>experimental feature
Check the scale UI box and restart photoshop.