Concept of pituitary microadenoma.
Clinically, pituitary tumors ≤10 mm in diameter are referred to as pituitary microadenomas, and the diagnosis is mostly established by imaging (CT or MRI) (pituitary tumors >10 mm in diameter are referred to as pituitary macroadenomas). Some pituitary microadenomas are found incidentally during CT or MRI of the head for other reasons, and the patient does not have any clinical symptoms of pituitary tumor and the pituitary endocrinology examination is completely normal. If the patient is asymptomatic, head-enhanced MRI should be repeated every 1 to 2 years.
For symptomatic pituitary microadenomas (mostly endocrinological symptoms, which may be accompanied by headache; pituitary microadenomas with visual effects are rare), patients, their families and clinicians should pay high attention to them.
Management strategies for pituitary microadenomas.
First, the patient’s clinical presentation combined with pituitary endocrinology and pituitary imaging can mostly identify the type of pituitary microadenoma, such as prolactin microadenoma, GH microadenoma, ACTH microadenoma or microadenoma with no obvious effect on secretory function (only headache, or mild menstrual disorder in young women).
Prolactin (PRL) microadenoma.
1.Preferred drug treatment
For infertile women with pituitary prolactin microadenoma, oral treatment with dopamine agonist DD cryptocryptine is generally available. With long-term treatment, the tumor size can be reduced and some patients can be cured. In young women who become pregnant after treatment with dopamine agonists, stroke or significant enlargement of the pituitary adenoma may occur during pregnancy, requiring emergency surgery if necessary. Long-term use of sniffing cryptine, some patients have difficulty to stick to it due to heavy side effects, in this case, surgery can also be an option.
2.Trans-pituitary sinus surgery
Surgery is the most fundamental treatment for patients who are drug intolerant or dopamine agonist resistant. The success of surgery depends critically on the experience of the operator, the size and aggressiveness of the tumor, and 60% to 90% of patients achieve normal prolactin levels after surgery. Therefore, it is reasonable for patients to choose surgical treatment. The most important prerequisite, of course, is the low mortality rate of transsphenoidal surgery and the low chance that the surgery will affect normal pituitary function, the latter being very important in patients who want to have children. It is worth noting that long-term treatment with dopamine agonists may affect the efficacy of the procedure. The introduction of endoscopic technology into transsphenoidal surgery results in less trauma, almost no damage to the nasal cavity, better intraoperative visualization, more complete tumor removal, better protection of the normal pituitary gland, faster patient recovery, more comfort during recovery, and better surgical results.
3.Follow-up observation
Longitudinal studies have shown that only 7% of prolactin microadenomas can develop into larger tumor lesions. Therefore, for patients with prolactin microadenoma, if they have normal menstrual cycle and libido, and if they have mild overflow of breast milk and are not planning to get pregnant, they can be followed up and observed without immediate treatment.
Growth hormone (GH) microadenoma.
1. Preferred surgical treatment
Transsphenoidal sinus surgery is the preferred treatment for patients with GH microadenoma and has a good effect; more than 2/3 of patients can have their GH reduced to normal levels after surgery.
2.Drug treatment
Growth hormone mimetic drugs, such as octreotide, santorum, etc. These drugs can reduce blood GH and IGF-1 to normal level in 50%~60% of patients and can improve symptoms in more than 90% of patients. The drugs are more expensive. The main side effects are gastrointestinal reactions and gallbladder stones.
3.Radiation therapy
Radiation therapy can be chosen for patients who have contraindications to surgery or for patients with residual tumor after surgery. Radiotherapy has relatively good effect on GH microadenoma, 60%-90% of GH adenoma are more sensitive to radiotherapy. Most of them achieve significant results in about 2 years, but up to 40% of them have hypopituitarism after radiotherapy. It is contraindicated in patients with visual field defects and intracranial hypertension.
Adrenocorticotropic hormone (ACTH) microadenomas.
Surgery is the preferred method of treatment. Selective transsphenoidal microadenectomy can achieve endocrinological remission in 95% of patients, and normal anterior pituitary function can be restored. Sometimes only normal or hyperplastic pituitary tissue is removed, but complete remission can be achieved in 2/3 of patients after surgery.
Microadenomas with no significant functional effects.
The principle of management is regular follow-up. In the absence of pressure or endocrinological manifestations, treatment, especially surgery, need not be considered at all.
In conclusion, the treatment of pituitary microadenomas should be individualized. Some patients require only follow-up, some patients require transsphenoidal sinus surgery, and some patients have pharmacological treatment as the first choice.