What Is a Pituitary Microadenoma?

Pituitary microadenomas refer to pituitary adenomas with a diameter of 10 mm or less. They originate in the anterior pituitary gland and are mostly functional pituitary tumors. They are benign tumors.

Pituitary microadenomas refer to pituitary adenomas with a diameter of 10 mm or less. They originate in the anterior pituitary gland and are mostly functional pituitary tumors. They are benign tumors.

Chinese name

Pituitary adenoma

Foreign name

pituitary microadenoma

Etiology and common diseases of pituitary microadenomas :

Most pituitary adenomas show expansive growth. The cause of the disease is unclear, and it may be related to genetic factors, physical and chemical factors, and biological factors. It can be divided into functional and non-functional according to whether it secretes hormones. Most have no endocrine function and are nonfunctional adenomas. A few functional adenomas can cause elevated endocrine hormone levels and cause clinical symptoms. The most common are amenorrhea, lactation and infertility caused by elevated prolactin. Nonfunctional adenomas have no clinical manifestations, but there is a possibility of growth and stroke, which can cause symptoms of local compression.

Differential diagnosis of pituitary adenoma :

The diagnosis of pituitary adenomas is mainly based on the patient's clinical manifestations, visual field disturbances and other neurological findings, as well as endocrine and radiological examinations. Typical pituitary tumors are not difficult to diagnose. However, in early pituitary tumors, when the symptoms are not obvious, the diagnosis is not easy, and even cannot be found.

The clinical manifestations are related to the patient's gender, age, tumor size and expansion direction, and type of hormone secretion, including the following 4 groups of symptoms:

1. Pituitary tumors cause symptoms and signs caused by excessive secretion of hormones. Common cases are acromegaly, Cushing's syndrome and prolactinoma.

2. The pituitary compression group, mainly the reduction of pituitary hormone secretion, generally affects growth hormone GH first, followed by luteinizing hormone, follicle stimulating hormone, and finally adrenocorticotropic hormone, thyroid stimulating hormone, a few may be accompanied by diabetes insipidus .

3. Compression syndromes around the pituitary gland, including headaches, decreased vision, visual field defects, hypothalamic syndrome and cerebrospinal fluid rhinorrhea.

4. Pituitary apoplexy refers to pituitary adenoma and / or pituitary infarction, necrosis or hemorrhage. Compression symptoms and meningeal irritation symptoms can quickly appear clinically. The clinical manifestations of hyperpituitarism can disappear or be reduced, and even anterior pituitary function is low Less.

Pituitary microadenomas examination:

(I) Endocrinology examination:

Using endocrine radioimmunomicro-quantitative method to directly determine growth hormone, prolactin, adrenocorticotropic hormone, thyroid stimulating hormone, melanin stimulating hormone, follicle stimulating hormone, luteinizing hormone, etc. Great help.

(2) Imaging inspection:

Imaging examination is a necessary method for the diagnosis of pituitary microadenomas. Not only can the lesion be localized, but also its size, number, morphology, edge, density (signal) characteristics and its relationship with adjacent structures can be evaluated.

1. Magnetic resonance imaging has high resolution of soft tissues and no bone artifacts. It is the best imaging method for saddle lesions. With 2 to 3 mm thin-layer scanning, the morphological characteristics of the lesion can be displayed from the coronal, sagittal and transverse positions. Through multi-parameter and multi-sequence scanning, the signal characteristics of the lesion can be displayed, and it can also be determined whether there are components such as bleeding, cystic change, and fat in the lesion. In conventional MRI images, pituitary microadenomas show slightly longer T1 and slightly longer T2 signals, which are significantly different from the iso-T1 and iso-T2 signals of normal pituitary tissue, and there is no change in the signal in the fat suppression sequence. Under normal circumstances, morphological changes in the pituitary gland at the lesion site, such as hump of the upper edge of the pituitary gland, depression of the saddle bottom, lateral displacement of the pituitary stem, and involvement of the cavernous sinus. However, due to the small volume of some pituitary adenomas, the morphological changes are not significant, and part of the volume effect makes the signal of the lesion site compared with normal pituitary tissue, which is not conducive to displaying the saddle image of the lesion as one of the basic examinations. When the pituitary tumor is very small, there is no change in the saddle. As the tumor grows, it can lead to the enlargement of the saddle, bone destruction, and invasion of the saddle.

2. Although spiral CT is the most commonly used imaging method for craniocerebral examination, its soft tissue resolution is low, and skull base artifacts are more, which affects the observation of lesions in the saddle area. It also shows poor display of pituitary adenomas. It is difficult to fully display the imaging characteristics of pituitary microadenomas. The CT examination was enhanced with intravenous contrast, and showed a pituitary adenoma with a size of 5 mm. Smaller tumors still show difficulties.

Pituitary microadenomas treatment principles:

(A) surgical treatment:

Including craniotomy and transsphenoidal surgery.

(B) radiation therapy:

It has certain effects on pituitary adenomas. It can control the development of tumors and sometimes shrink the tumors, resulting in improved visual field, but it cannot be cured completely.

(Three) drug treatment:

Bromocriptine is a semi-synthetic ergotamine alkaloid, which can stimulate dopamine receptors in pituitary cells and reduce the effect of prolactin in the blood. After taking bromocriptine, the prolactin adenoma can be reduced, menstruation and ovulation can be resumed, and the galactorrhea can be suppressed. However, bromocriptine cannot cure the prolactin adenoma at all. After stopping the drug, it can continue to increase and the symptoms reappear. In addition, bromocriptine can also reduce the symptoms of growth hormone cell adenomas, but the dose is large and the effect is poor.

Prevention of infection and symptomatic treatment, and those with complications should deal with the complications. To correct cerebral edema and reduce intracranial pressure, 20% mannitol, furosemide, dexamethasone are the main drugs, and even human albumin can be used. Pay attention to the balance of electrolytes and body fluids, and replenish blood loss during the operation.