Prolactinoma is the most common benign tumor of the pituitary gland .
The presentation of prolactinoma is based on the hormonal effects secondary to hyperprolactinemia and the space-occupying effects of the growing tumor. The major clinical features, which vary according to the duration and degree of the pathological condition and the age and sex of the patient, usually include:
The following related effects also occur with a certain frequency:
The workup of prolactinoma is largely based on laboratory studies and imaging tests.
The laboratory studies necessary to diagnose prolactinoma include several hormone tests  to analyze the major key hormones secreted by the pituitary gland. These certainly include serum prolactine (PRL) levels, which should not be measured soon after pregnancy and always combined with pregnancy test in female patients, as pregnancy itself might be a cause of secondary amenorrhea. The levels of thyroid-stimulating hormone should also be measured, since this compound might cause a marked increase in PRL levels. Other hormones to test are:
To these other appropriate laboratory tests should be added, when there is the possibility of other systemic causes for hyperprolactemia as chronic renal failure and liver cirrhosis.
The most important imaging tests employed in the diagnosis of prolactinoma are MRI and CT scans, which are used to determine whether or not a tumor is present, its size, and the extent of its possible encroachment on the surrounding healthy structures. These scans should be repeated in the postoperative and follow-up phase, to follow the progress of the tumor and try to avoid further severe complications.
The major goals of the treatment of prolactinoma are to bring the prolactin secretion back to normal levels, restore the pituitary gland function, reduce the tumor size as well as adjust the visual anomalies occurred during the tumor development. It is paramount to rule out any other cause for the elevation of prolactin levels, like stress which might easily be addressed by increasing the physical exercise.
The treatment of prolactinoma is largely based on the use of dopamine agonists, which appears to be effective in around 80% of the cases. Among these, bromocriptine and cabergoline are the most commonly used, even though they are frequently associated with serious side effects like nausea, dizziness, and hypertension, especially when the patients already have low blood pressure levels before starting the treatment itself. These side effects are less common and less severe with cabergoline than with bromocriptine, but as its half-life is quite long (4-7 days) it might inadvertently affect the ability of the patient to keep blood pressure within the correct physiological range, which in turn might cause discomfort and fainting. To reduce these side effects doctors are advised to start treatment very slowly.
Surgery might also be used in the treatment of prolactinoma, but only when medical treatment is not tolerated by the patients or when it fails to produce a positive outcome in terms of reduced prolactin levels, restored pituitary function, and reduced tumor size.
The patients affected by microprolactinoma usually have an excellent prognosis, since in 95% of the cases the tumor does not enlarge when monitored over a follow-up period of 4 to 6 years from the diagnosis.
On the contrary, the patients affected by macroprolactinoma have a worse prognosis due to the fact that their tumor tends to grow over time. Therefore, a much more aggressive treatment is required to avoid further complications, which should be regulated according to the tumor growth rate. The growth rate itself varies from individual to individual, and cannot be predicted with accuracy and in a reliable manner. In these cases, monitoring of clinical signs and measurements of serum prolactin levels are highly recommended .
Despite research, the cause of prolactinoma still remains largely unknown, although according to several studies, stress might play an pivotal role in its development as it can significantly increase prolactin levels. As all the pituitary adenomas, prolactinoma is monoclonal in origin , resulting from the uncontrolled proliferation of single mutated pituitary cells. Many genetic studies reveal that a great deal of mutations appear in the aryl hydrocarbon receptor-interacting protein (AIP) gene, which occur very early in life (less than 30 years of age), are invasive in nature, have a suprasellar extension and appear to be resistant to dopamine agonist treatment  . Rarely prolactinomas occur in association with multiple endocrine neoplasia type 1 (MEN 1) syndrome.
Representing around 40% of all tumors occurring in the pituitary gland, prolactinoma is undoubtedly the most common type of pituitary adenoma. Its prevalence is unknown in the US, but according to a study made in Belgium, this should be around 620 cases per million inhabitants .
This tumor appears much more frequently in women than men, with an estimated ratio of frequency between the two genders of 10:1 . In women prolactinoma tends to occur especially during childbearing years, with a peak incidence between the second and third decades of life. This sex imbalance disappears in advanced ages, especially after the fifth decade of life, when the frequencies of prolactinoma occurrence in men and women become very similar . Furthermore, women tend to be affected by microadenomas while men by macroadenomas.
The tumor transformation taking place in prolactinoma is the result of a neoplasmatic alteration which always occurs in the anterior pituitary lactotrophs, and, as previously mentioned, it is frequently linked to mutations appearing in the aryl hydrocarbon-interacting protein gene.
The outcome of this transformation is the elevated synthesis and secretion of the prolactin hormone, which in normal physiological conditions is regulated by hypothalamic factors. These can be divided in two major groups, prolactin-releasing factors (PRFs), like for example dopamine, and prolactin-inhibitory factors (PIFs), like thyrotropin-releasing hormone or vasoactive intestinal peptide. The concentrations of these compounds are constantly regulated, so that there is always a proper balance among them which keeps the prolactin levels in the serum within the correct physiological range. This balance is also influenced by a variety of neurohormonal factors which determine the pulsative secretion of prolactin from the pituitary gland. When a prolactinoma develops this balance is disrupted, to be replaced by an elevated secretion of prolactin in a condition known as hyperprolactinemia     .
As the etiology of prolactinoma still remains largely unknown, no preventive measures can be suggested, apart from genetic testing in early age (less the 40 years of age) to detect any mutation in key genes such as hydrocarbon receptor-interacting protein (AIP) gene.
The pituitary gland is an endocrine gland situated at the bottom of the hypothalamus. It is also reffered to as hypophysis and is responsible for the secretion of a number of hormones regulating several aspects of the human body metabolism and functions, such as growth, blood pressure, lactation (formation of breast milk) and internal temperature regulation. One of the most important of these hormones, playing a pivotal role in lactation, is prolactin, which enables female mammals to produce milk in response to a variety of stimuli like eating, mating, ovulation, and nursing. Following a circular pattern, prolactin levels increase during pregnancy and childbirth and decrease once breastfeeding is discontinued. In men, prolactin is responsible for the sexual refractory period after having an orgasm, a temporary interval during which men cannot experience another orgasm despite receiving sexual stimulation.
Prolactinoma is the most common form of benign (non-cancerous) tumor of the pituitary gland. Despite research, the cause of prolactinoma still remains largely unknown, although according to several studies stress might play a role in its development. Representing around 40% of all tumors occurring in the pituitary gland, prolactinoma is undoubtedly the most common type of pituitary tumor.
The outcome of this tumor is an elevated production and secretion of the hormone prolactin, which in normal physiological conditions is regulated by hypothalamic factors. The signs and symptoms of prolactinoma are based on the hormonal effects of elevated prolactin and the space-occupying effects of the growing tumor itself, and the major clinical features include menstrual disturbance, infertility, spontaneous flow of milk from the breast, hypogonadism, as well as headache, dizziness and visual problems.
The treatment of prolactinoma is largely based on the use of dopamine agonists, which appears to be effective in around 80% of the cases. Surgery might be used in the treatment of prolactinoma, but only when medical treatment is not tolerated or when it fails to produce a positive outcome in terms of reduced prolactin levels, restored pituitary function, and reduced tumor size.
As the etiology of prolactionoma is mostly unknown, no preventive measure can be suggested, apart from genetic testing for the major mutations involved in its development.