When calcium levels in the blood are too low, the body releases a hormone that removes calcium from the bones. A person who suffers from a certain type of thyroid disease will often have low blood calcium and brittle bones because the body is taking the calcium from the bones. The afflicted person will typically see an endocrinologist, who studies hormones, and an orthopedist, who studies bones. What do these two doctors have in common

They both would need to check the calcium levels

Explanation:

The two doctors would both need to check the calcium levels of the patient.

While the endocrinologist would need to check the calcium level in the blood, the orthopedist would have to check the calcium level in the bones of the patient.

Most endocrine disorders are caused by abnormal calcium levels in the blood while the bones are largely made of calcium. Hence, both doctors would usually need to work with the calcium levels in the blood and bones respectively.