The other possibilities are iron deficiency anemia, hepatic failure, cirrhosis, diabetes mellitus, congestive heart failure and hyperthyroidism. If the nail
is crumbling then a fungal nail infection
caused by onychomycosis needs to be ruled out.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps.