This article is from the Rottweilers Breed FAQ, by email@example.com (Denise Gross).
Hypothyroidism refers to insufficient output of the thyroid hormone by
the thyroid gland. It may slow down the whole body functions; the dog
may become lethargic, mentally slow, without much energy. Its coat may
become dull, thin and fall out easily. In males it can lower the sperm
count and reduce sexual activity. In females it may cause irregular
heat cycles. The signs may develop very slowly, and the condition can
be detected with a blood test. Usually, it is a permanent condition,
and is treated with thyroid hormones. Hypothyroid is generally
considered to be an inherited trait.