Lady has hypothyroidism. (Lady has everything.)
The classic signs are hair loss and lethargy. Being overweight and sensitive to cold are also signs. Lady had all four.
Here is a great article:
Hypothyroidism: A Case of Hypothyroid Disease in the Dog at ThePetCenter.com
It's very easy to diagnose with a T-4 panel. It's simple to treat, too, with just two pills a day. It's less than $5 a month to treat it.
Lady just has to have a thyroid panel done twice a year to make sure her dosage is still right. That's it. All her symptoms went away.