Spoon-shaped nails: Iron deficiency; thyroid disease.
Club-like nails growing around swollen finger ends: Chronic respiratory or heart problems; cirrhosis of the liver.
Horizontal ridges: Injury; infection; nutrition.
Longitudinal ridges: Aging, poor absorption of vitamins and minerals; thyroid disease; kidney failure.
Infected nails (red, tender, swollen, pus): Bacterial or yeast infection.
Overlarge moons: Overactive thyroid; genetics; self-induced trauma (habit tick).
No moons: Underactive thyroid; genetics.