The different types of pituitary adenomas
There are several histological subtypes corresponding to different clinical presentations:
Secreting or functional adenomas
- The corticotroph adenoma is most often a microadenoma (<10mm) and secretes ACTH. It accounts for 6% of all adenomas. It is rare, affecting 1 to 6 people per million inhabitants per year. The average age at diagnosis is 40, with a clear female predominance. It is responsible for Cushing’s disease. Macroadenomas are less frequent. Sometimes, although the pituitary origin is certain, MRI does not always identify the tumor. Surgery by an expert neurosurgeon is the first-line treatment.
- The somatotroph adenoma secretes growth hormone (GH). It accounts for about 6% of all adenomas. It is also rare, affecting 1 to 6 people per million inhabitants per year. The average age at diagnosis is 47. It is responsible for Acromegaly. Given the insidious development of clinical signs, diagnosis is often delayed (often by 4 to 10 years). In some cases, the adenoma co-secretes growth hormone and prolactin (mixed GH-PRL adenoma). Surgery by an expert neurosurgeon is often proposed as first-line treatment. Complementary medical treatment may be indicated (somatostatin analogs).
- The prolactin adenoma (prolactinoma) is the most frequent of pituitary adenomas. It accounts for 60% of all adenomas. Its prevalence is around 1/2000. The average age at diagnosis is 32, with a clear female predominance (female-male ratio: 10/1). Medical treatment is often proposed as first-line therapy (dopamine agonists). In certain cases of small, well-defined, and non-invasive prolactinomas, surgery may also be discussed.
- The thyrotroph adenoma secretes TSH. It is very rare (<1% of all adenomas). It is most often accompanied by signs of hyperthyroidism. Depending on the existence of cavernous sinus invasion, treatment can be surgical or medical.
Non-secreting or non-functional adenomas
They account for 30% of pituitary adenomas. These tumors are mostly gonadotroph adenomas.
The term “non-functional” is more appropriate because, in about one-third of cases, there is hormonal expression during histological analysis of the sample (obtained during surgery), although there is no clinical impact (silent adenomas).
Silent adenomas
These are adenomas that express hypersecretion during histological analysis (positive staining for ACTH, PRL and/or GH and/or TSH). However, these adenomas do not lead to a specific clinical picture of hypersecretion.
These adenomas may tend to proliferate slightly faster, justifying more frequent MRI monitoring during follow-up.
Aggressive adenomas
The frequency of aggressive adenomas is very low (<1%). Aggressive adenomas increase in volume despite the combination of standard treatments (surgery, medical treatment, and radiotherapy). Only 0.2% of pituitary tumors present metastases during their course.
Chemotherapy treatment is recommended, implemented in an expert center.