While prolactinomas are relatively rare, misdiagnosis of the condition is not. There will be several hundred new cases of large prolactinomas (also called “giant prolactinoma” or “macroprolactinoma”) diagnosed this year in the United States. Large prolactinomas may first present with symptoms of pressure within the head, such as headache or visual disturbances. Because a prolactinoma is a pituitary tumor that affects hormone function, both small and large prolactinomas may present with signs of hormonal imbalances such as breast enlargement, gonad shrinkage or breast milk production.
Once prolactinoma is suspected, imaging is typically done. However, imaging cannot conclusively determine whether a mass is a prolactinoma, another pituitary tumor or some other type of tumor.
A critical part of the testing for prolactinoma is a blood test for elevated prolactin levels, a hormone produced by the pituitary gland. Interestingly, these blood tests must be performed on more than one occasion because hormone levels can be adversely affected by a variety of factors, including the time of day that the test is performed, diet and even lunar cycles.
Currently, the blood test for prolactinoma is effective for diagnosing smaller prolactinomas. However, larger tumors produce so much prolactin that the serum prolactin level may actually appear normal, low or only slightly elevated. This phenomenon is called the “hook effect.” Hook effects are relatively common and well-known among endocrinology experts. A special laboratory test must be ordered to account for the hook effect when a large prolactinoma is suspected.
When a large prolactinoma is misdiagnosed as another type of tumor, devastating consequences can ensue. Most prolactinomas can be treated with medicines that shrink the tumor and relieve its symptoms. However, when there is a misdiagnosis, surgery may be ordered. Unnecessary surgery to remove a prolactinoma carries many otherwise avoidable risks, such a brain injury, nerve damage, blindness, infection, stroke and death.
Medical malpractice claims arise under Ohio law when a physician fails to follow accepted standards of medical care. When it comes to misdiagnosing a large prolactinoma, there are two potential types of medical negligence: (1) a surgeon failing to consult an endocrinologist; and (2) an endocrinologist failing to order specific lab testing to account for a potential false negative due to the hook effect.
