Do you shrink if you drink coffee?

No, although it seems highly believable it is just a myth.

Coffee contains caffeine, which can increase calcium loss in urine. Some scientists have suggested that a high caffeine intake is a risk factor for osteoporosis. In one study, drinking one cup of coffee caused an extra six mg of calcium to be lost, suggesting that drinking one to two cups of coffee a day will not greatly affect your calcium levels. However, statistics show that drinking more than four cups of coffee each day doubles the risk of hip fracture.