Pituitary adenomas are tumors that originate in the pituitary gland.
The anterior pituitary gland is made up of the anterior and posterior lobes. The pituitary gland is located in the pterygoid saddle and is covered by the saddle septum, but a pituitary stalk crosses the saddle septum and is closely connected to the lower thalamus.
Pituitary tumor refers to the tumor in the anterior pituitary gland (glandular part), which is one of the common intracranial tumors in adults. As the tumor grows in the saddle, it can compress the normal pituitary gland and pass upward through the septum to compress the optic cross or optic nerve. In addition, other symptoms and signs may occur due to tumor expansion and compression of adjacent tissues. Most pituitary adenomas are slow-growing benign tumors and adenomas are rare. Pituitary adenomas can be clinically and pathologically classified into four categories: suspicious, eosinophilic, basophilic, and mixed according to the nature of cell staining.
Their clinical features are as follows.
1.Signs and symptoms of optic nerve compression
As the tumor grows in the pterygoid saddle, the upward development will compress the optic cross or optic nerve and cause the change of vision and visual field. 90% of patients have vision loss, or even monocular vision loss, or even blindness in one or both eyes. The change of visual field may vary depending on the compression of the nerve or optic cross. If the optic cross is compressed, it may produce bilateral temporal hemianopia or temporal blindness in one eye. More than 70% of patients have fundus changes. The majority of patients have primary optic nerve atrophy, the extent of which varies depending on the degree of optic nerve compression, from the optic papillary tinge to the typical primary optic nerve atrophy. Only a few cases have optic nerve papillary edema due to increased intracranial pressure.
2.Signs and symptoms of endocrine and metabolic disorders
The endocrine function of the pituitary gland is very complex, mainly under the domination of the central nervous system, through the endocrine control of human growth, development, material metabolism and sex organs, sexual function and other physiological activities regulation. The anterior pituitary gland is known to secrete six hormones, namely growth hormone, adrenocorticotropic hormone, prolactin, thyroid stimulating hormone and two gonadotropins. The eosinophilic and basophilic adenoma cells themselves have endocrine function and can cause excessive hormone levels and hyperfunction of pituitary gland, but the tumor can also squeeze the normal pituitary gland and cause hypopituitary function. In addition, the tumor can involve the hypothalamus upward and the posterior pituitary gland backward. The posterior pituitary gland contains antidiuretic hormone and oxytocin, so the involvement of posterior pituitary gland can lead to uremia.
3.Low pituitary function
The degree of hypopituitarism is related to the degree of pressure on the normal pituitary gland cells. As a result of hypopituitarism, the endocrine glands under its control are atrophied and show various dysfunctions.
(1) Hypogonadism and changes in secondary sexual characteristics: due to hypogonadism, in men, it manifests as hypogonadism, impotence, testicular atrophy, scarce beard, loss of pubic hair, axillary hair and subcutaneous fat deposition, the skin becomes delicate and feminine. In female patients, the symptoms include menstrual disorders, amenorrhea, atrophy of the uterus and adnexa, breast atrophy, hair loss, loss of sexual desire, and lack of lactation after childbirth.
(2) Hypothyroidism: manifestations include chilliness, drowsiness, depression, loss of appetite, fatigue, amenorrhea, non-digital edema, dry skin, low sweating, low basal metabolic rate, susceptibility to infection, and reduced absorption of serum protein-bound iodine.
(3) Hypoadrenocorticism: often less pronounced. More common are physical weakness, easy fatigue, low resistance, easy to catch cold, loss of appetite, weight loss, small pulse, low blood pressure, low blood sugar, etc.. However, there is no effect on electrolyte metabolism. Urinary excretion of 17 ketones and 17 hydroxysteroids is also lower than normal.
Pituitary adenomas or eosinophilic adenomas often show hypopituitarism in the late stage.
4.Pituitary hyperfunction
Eosinophils can produce growth hormone and prolactin. Basophilic cells produce thyrotropic hormone, adrenal hormone and gonadotropin. Therefore, these tumors can cause hyperpituitarism, especially in the early stages. Although eosinophilic adenomas can have excessive secretion of growth hormone, they can squeeze basophils, causing them to be hypofunctional.
(1) Hyperproduction of growth hormone: If eosinophilic pituitary adenoma occurs before epiphyseal closure (before adulthood), it is called gigantism, and if it develops in adulthood, it is called acromegaly, and the type in between is mixed. In gigantism, the body is tall and muscular, the sexual organs develop early, the basal metabolism is often higher than normal, and the blood sugar is too high, the glucose tolerance is reduced, and a few patients have diabetes. When growth reaches its peak, it gradually begins to decline, with mental inactivity, mental retardation, limb weakness, muscle relaxation, hair loss, decreased libido, often failure to develop, lower than normal metabolic rate, and slow heart rate. In adult onset, because the epiphysis has healed, it is manifested as acromegaly, and the related symptoms and signs gradually appear, such as head and face manifestation of jaw enlargement, lower lip thickening, ear and nose growing, tongue large and thick, eye sockets, forehead bone, zygomatic bone are enlarged, teeth are sparse, skull thickening, maxillary sinus and mastoid process enlarging, long bones of the limbs also become thick, fingers and toes thick and short, back of the hand thick and wide. The vertebrae are also widened, but often cause wedge-shaped changes due to osteoporosis, resulting in the deformity of back convexity and waist convexity. The skin is rough and thickened, with hyperpigmentation and increased hair, showing the external manifestation of male distribution.
(2) Hypergonadotropic: It causes the target glands to secrete more sex hormones, and men may have hyperactive sexual function at the beginning, and then gradually decline. In women, menstruation is less frequent, amenorrhea is present, breasts are well developed, and lactation can be prolonged until several years after lactation has stopped.
Hyperthyroid hormone: Patients often have an enlarged thyroid gland, a few patients have hyperthyroidism, an increased basal metabolic rate, but sometimes it can be reduced, and increased blood cholesterol.
(3) Hyperadrenocorticotropic hormone: The target gland secretes too much adrenocorticotropic hormone, the adrenal glands are enlarged, and a few patients have adrenocortical adenoma formation. These manifestations are not only related to adrenal hormone, but also to growth hormone.
(4) Basophilic hyperfunction: thyrotropic, adrenal and gonadotropic hormones are affected, which can produce Cushing’s syndrome. Patients show centripetal obesity, more obvious in face, neck and trunk, relatively thin limbs, round face like full moon, red and fatty, often with acne, fatty deposits in upper back, thin skin with purple lines, marble-like. Osteoporosis, easy to fracture, can also cause rickets, back pain, chest pain. Most patients have diabetes mellitus, but only 1 / 3 to 1 / 4 of them are clinically symptomatic. Patients may have sodium and water retention, increased excretion of nitrogen and potassium, water retention and hypertension. Some female patients have amenorrhea, enlarged clitoris, hairiness, and masculinity. In men, there is impotence and loss of libido.
5.Symptoms of posterior pituitary and subthalamic involvement
If the tumor affects the posterior pituitary gland or lower thalamus, it may produce salivation, polyhydramnios, polyuria, hypothermia, and disorders of water, electrolyte and fat metabolism.
6.Signs and symptoms of headache and increased intracranial pressure
Pituitary adenoma often causes headache, and a few patients have headache, vomiting and optic nerve papillary edema due to the tumor protruding into the anterior part of the third ventricle and causing intracranial pressure increase. However, most pituitary adenomas do not cause headache due to increased intracranial pressure. Their headache may be caused by increased tension in the saddle diaphragm due to tumor growth in the saddle, or due to involvement of sensitive structures such as meninges, blood vessels and nerves. In addition, headache may also be caused by thickening of skull and bone growth affecting meninges and blood vessels. Patients with eosinophilic pituitary adenoma not only have intractable headache, but also often have pain in the extremities and spine.
7.Other symptoms and signs
(1) If the tumor develops into the anterior part of the third ventricle, it will cause interventricular foramen obstruction, which may affect the lower thalamus or posterior pituitary lobe and cause uremia, drowsiness, coma and thermoregulation disorder.
(2) The tumor may develop to the saddle side, and in addition to compressing the optic nerve or optic tract, it may also compress the cavernous sinus, resulting in unilateral protrusion of the eye and involvement of the first branch of cranial nerves III, IV, VI and V. The involvement of cranial nerve III is most common.
(3) The tumor erodes the saddle base and may cause cerebrospinal fluid nasal leakage.
(4) If the tumor extends to the frontal and temporal lobes, epilepsy, hemiparesis, cone fasciculation, olfactory disturbance, psychiatric symptoms and hallucinations may occur. However, it is rare in clinical practice.
(5) Pituitary stroke: Because of the solid bone wall of the pterygoid saddle, fast-growing pituitary adenomas (mostly eosinophilic adenomas) are restricted by the bone wall, which increases the intra-tumor pressure and leads to vascular atresia or thrombosis, thus causing hemorrhage and necrosis in part or all of the tumor. The clinical manifestations of pituitary stroke are characterized by sudden onset of severe headache, vomiting, cervical muscle tonicity, drowsiness or coma, and rapid visual loss, including sudden blindness of one or both eyes, or impairment of III, IV, or VI cranial nerves, and even hemiparesis due to involvement of one internal carotid artery. In the case of subthalamic compression, drowsiness and hypothermia may occur. Hypopituitarism and secondary adrenocortical insufficiency may also occur. Lumbar puncture often contains blood in the cerebrospinal fluid.
The main treatment methods are surgery and radiation therapy.
(1) Surgery: The efficacy of transsphenoidal saddle surgery carried out in recent years has been greatly improved compared with the past, and the risk of surgery has been significantly reduced, so the indications for pituitary tumor surgery are wider than before. The following conditions should be treated surgically: (1) impaired vision and visual field; (2) cranial nerve compression, diplopia and limited eye movement; (3) large tumor size; (4) pituitary stroke; (5) increased intracranial pressure; (6) recurrence after radiotherapy; (7) diagnostic investigation.
(2) Radiation therapy: Radiation therapy has certain effect on non-functional pituitary tumor. The tumor is moderately sensitive to radiotherapy, and the therapeutic effect can be shown only after several months, and it takes one year or more to achieve the maximum effect. The indications for radiotherapy are as follows: (1) the tumor is small in size and the vision and visual field are affected at the end; (2) the patient is in poor general condition, old and frail, and has other diseases that cannot tolerate surgery; (2) the tumor cannot be removed by surgery and there are residual tumor tissues.
(3) Hormone replacement therapy: For patients with anterior pituitary hypoplasia, exogenous hormones should be supplemented to correct endocrine disorders. For those who need surgery or radiotherapy, endocrine disorders should be corrected with drugs before these treatments, so as to improve the systemic metabolic condition, enhance the physical fitness and resistance, which will help the surgery or radiotherapy to proceed smoothly and improve the safety factor.