don't know Masullo, insignificant maybe.. but also your weight is different depening on your location in the world, and whether or not it's a full moon.. maybe time of day too?
I should think your "real height" should be measured after you have been up walking for a while. After a time when all joints in your back have compressed again etc. As for height variation it must a few millimeters at the most!
apparently when you are asleep, due to the fact that you are lying down and there is no weight on your spine, the cartilage in between your vertebrae, expand, causing you to be taller in the mornings when you wake up, than when you have been walking around!
The average human is about 20mm shorter by the end of the day compared to when they get up. This is due to the flexible intervertebral discs compressing as the day goes on. This happens as the spine has about 50kg of pressure put on it just holding you upright.