Veterinarian perscribed melatonin?

[Puppy182]

Hi, about a year ago our dog (a 4 year old boxer) was diagnosed with hypothyroidism and perscribed thyroxin. We recently decided to take her to another office to get a second opinion on the proper dosage as the bald spots on the back of her body were not improving. Anyway, we recieved a call today from the Veterinarian about the results of her blood work and she said that her t-4 levels were almost normal and therefore did not recommend thyroxin at this time and instead suggested that we put her on 5mg of melatonin daily and then check back in a month and see if the symptoms improve. Now by what she said i assumed that melatonin was a drug that would help our dog with her hair loss problem, but when i researched it online it said thisis often perscribed for dogs with anxiety problems... which i do not believe my dog has. She was very anxious at the vets office, but this is not how she typically acts at home. I really don't think i should be giving her this drug because she is already displaying symptoms of hypo- such as low energy- and i am afraid that the melatonin will completely sedate her! What should i do?