Pituitary adenomas are benign tumors from the parenchymatic cells of the anterior pituitary gland ( adenohypophysis ) or the posterior pituitary gland ( neurohypophysis ). They make up 10–15% of all intracranial neoplasms. Women are affected more often (3: 2) than men.
The division is based on the size into macro and microadenomas. If they measure less than 1 cm in diameter, they are clinically referred to as a microadenoma . Larger tumors are called macroadenomas .
- Grade 0: Small tumor within the pituitary gland
- Grade I: Minor bulging with an intact bony floor of the sella turcica
- Grade II: soil intact, sella turcica more than 10 mm enlarged (non-invasive)
- Grade III: Partial destruction of the bony floor with penetration of the tumor into the sphenoid sinus (invasive)
- Grade IV: Complete destruction of the soil with diffuse infiltration of the sinus.
Extrasellar upward expansion is classified into symmetrical (A – C) and asymmetrical (D + E) expansions, depending on the extent to which they are advanced.
A further classification is based on whether the tumors produce more hormones. If they are secreting pituitary hormones, they can be recognized by the hormone side effects at this stage. A distinction is thus made between hormone-active and hormone-inactive adenomas.
- Prolactinoma (prolactin producing adenoma) 30% of cases
- Growth hormone producing (somatotropin) adenoma 10–20%
- Mammosomatotropic Adenoma (Somatotropin and Prolactin)
- Acidophilic stem cell adenoma
- Corticotropic Adenoma (ACTH) 10%
- Gonadotropic Adenoma (FSH-LH) 10%
- Thyrotropic adenoma (TSH) 1%
- Plurihormonal adenoma
- Null cell adenoma / oncocytoma ( rich in mitochondria )
- Non functioning adenoma (NFA) (does not produce any hormone in clinically relevant quantities)
Symptoms of all pituitary tumors can be restrictions of the field of vision - here especially bitemporal hemianopia - or headaches . If the III. Cerebral ventricle , hydrocephalus can develop. The cranial nerves oculomotorius (eye muscle nerve ) and the first two branches of the trigeminal nerve , the ophthalmic nerve and the maxillary nerve are also at risk due to the mostly unilateral growth . A narrowing of the internal carotid artery can also be observed.
Side effects of the hormone-active tumors result from the effects of the individual hormones. In the case of prolactin , galactorrhea is observed , in the cells that produce dense granules and acidophilic somatotropin -producing cells an acromegaly (or the gigantic hypophyseal growth, also known as gigantism), in ACTH -producing adenomas with basophilic cells, Cushing 's disease (Cushing's disease, basophildenoma, basophilism) ) with adrenal hyperplasia . Pituitary adenomas also occur in MEN 1 . The posterior lobe of the pituitary produces the antidiuretic hormone (ADH). In rare cases, thyrotropin (TSH) is produced in excess, which can lead to hyperthyroidism .
Hormone-inactive adenomas are usually discovered later due to the symptoms that set in later and are therefore larger at the initial diagnosis. The anterior pituitary lobe can be insufficiently supplied by the displacing growth, which leads to hormone deficiency symptoms. Anemia and increased, very fine furrowing of the skin are typical in men. The lack of thyroid hormones leads to the symptoms of hypothyroidism with increased fatigue, lack of drive and constipation . The symptoms can turn into the full picture of pituitary insufficiency . Very rarely, if the size is very large, epileptic seizures can occur.
According to the suspected clinical diagnosis, it is mainly the endocrinological symptoms that point to a pituitary adenoma. Examining the basal hormone levels in the blood can also be groundbreaking, especially growth hormone and prolactin . If an adenoma produces several hormones, it is called a mixed tumor.
Conventional X-rays show an enlargement of the sella turcica from a size of about 5 mm . The computed tomography covers only larger, mostly balloon-shaped pituitary adenomas in a safe place. Therefore, the method of choice is contrast-enhanced magnetic resonance imaging , which can also detect much smaller tumors. A field of view measurement should also be performed, as the tumor can compress the optic nerves.
In pituitary adenomas, cystic swellings (blisters) or necrotic (dead) sections are observed in 10% of cases . Calcium deposits are usually associated with prolactin-forming adenomas. Monomorphic , epithelial cells with a network of capillary vessels are observed microscopically . The cell nuclei are round to oval and contain a chromate structure .
Smaller, asymptomatic, hormone-inactive adenomas (“zero cell adenomas”) can make up up to 20% of all cases in autopsies .
In particular, prolactin-producing adenomas can be treated therapeutically with the dopamine agonist bromocriptine . Dopamine is a chemical messenger that the hypothalamus normally uses to prevent the pituitary gland from making too much prolactin. The tumors fibrosis and can occasionally shrink, but when the therapy is discontinued they sometimes grow again, so that an operation must then be performed. A therapy attempt with bromocriptine is also undertaken for growth hormone-producing adenomas. In the case of non-response, the alternative is also the surgical one.
Alternatively, surgical resection of the tumor is possible. This is done in a transsphenoidal way through the nose; a craniotomy is only performed for larger tumors , in which the skullcap has to be opened. Regular magnetic resonance imaging (MRI) is extremely important for monitoring the course of treatment with dopamine agonists and after an operation on the pituitary gland.
It is important to monitor the hormone levels accordingly after treatment and, if necessary, to replace the lack of hormone production, especially after radical surgery. Thyroid hormones , gonadotropins and cortisol may be necessary . If central diabetes insipidus develops due to an ADH deficiency, this must be treated with desmopressin .
- Klaus Poeck, Werner Hacke: Neurology . 12th, updated and expanded edition. Springer, Heidelberg 2006, ISBN 3-540-29997-1 , pp. 322-326 .
- Ludwig Weissbecker: Diseases of the anterior pituitary gland. In: Ludwig Heilmeyer (ed.): Textbook of internal medicine. Springer-Verlag, Berlin / Göttingen / Heidelberg 1955; 2nd edition, ibid. 1961, pp. 999-1008, here: pp. 1004-1008 ( The hyperfunction of the anterior pituitary lobe ).