This is often a condition these small dogs inherit from their parents. Due to a failure of the blood supply to the neck of the femur (the 'ball' part of the hip) the neck decays and a fracture occurs. Severe lameness then results. Occasionally, lameness in the hind limbs has nothing to do with the legs at all.
Endocrinologists are doctors who specialize in the diagnosis and treatment of diseases of one or more glands. These doctors are well-trained experts who have studied the physiology and pathology of glands, and who provide care to patients with endocrine and metabolic diseases.
The adrenal gland is a small gland that makes steroid hormones, adrenaline, and noradrenaline. These hormones help control heart rate, blood pressure, and other important body functions. There are two adrenal glands, one on top of each kidney. Also called suprarenal gland. This answer is based on source material from the National Cancer Institute.