Introduction 

Prolactinoma is a non-cancerous tumour of the pituitary gland that results in excess secretion of prolactin, a hormone responsible for initiation and regulation of breast milk production. Prolactinomas can lead to reproductive issues like irregular menstrual periods, infertility, and sexual dysfunction. In cases of tumour growth, it can also exhibit symptoms such as headaches, vision problems and hormonal imbalances. Effects can differ between men and women, and between pre- and post-menopausal women. 

Prolactinomas account for up to 40% of all types of pituitary tumours, making them the most common one. They are more common in women than in men, with about 30 cases per 100,000 women and 10 cases per 100,000 men. They are most frequently diagnosed in women aged 25 to 34 years.¹

Headaches are a common symptom of prolactinoma impacting both men and women. Chronic headaches cause intense discomfort due to the persistent pain, disruption to daily life, reduce productivity, and impair concentration. This can lead to emotional distress and significantly diminish quality of life, emphasising the need for prompt diagnosis and effective management.

Understanding prolactinoma 

To gain a better insight into prolactinoma, it is essential to understand the pituitary gland, prolactin and the causes behind pituitary tumour development. The pituitary gland is located at the base of the brain and is the size of a pea. It secretes hormones such as growth hormone, adrenocorticotropic hormone, thyroid-stimulating hormone, and prolactin. The pituitary hormones are crucial in the regulation of various bodily functions, like growth, metabolism and reproductive functions.

Prolactin is primarily secreted by the front part of the pituitary gland and in a range of sites across the body including the uterus, breasts, prostate, skin and immune cells. It is vital in various reproductive, metabolic, immunoregulatory, osmoregulatory (regulation of body fluids) and behavioural functions. However, its main functions are milk production and mammary gland development within breast tissues in women. Serum prolactin levels range between 2-18 ng/ml and 2-30 ng/ml in males and most females respectively. During the third trimester of pregnancy, levels can be from 10–210 ng/ml. However, in case of prolactinomas, prolactin is typically higher than 200 ng/ml.

The exact cause of prolactinomas is still unknown. In some cases, genetic factors can increase predisposition of individuals. For instance, multiple endocrine neoplasia type 1 (MEN1) increases the risk of prolactinoma.

Symptoms of prolactinoma

Prolactinoma symptoms are either due to the high levels of prolactin in circulation or the tumour pressing on surrounding tissues. In pre-menopausal women, excess prolactin could cause abnormal production of breast milk, breast enlargement and tenderness, irregular or complete absence of menstrual periods and infertility. Post-menopausal women are less sensitive to prolactin and therefore experience symptoms that occur due to growth of tumour and compression of pituitary gland. This could lead to loss of normal hormonal function and cause hypothyroidism and in extreme cases low cortisol levels.In men, increased levels of prolactin result in low testosterone which consequently leads to decreased libido, erectile dysfunction, impotence, and occasionally, breast enlargement and tenderness.

Enlargement of the tumour causes pressure on surrounding tissues in the pituitary gland, resulting in headaches, a common symptom of prolactinoma. The tumour could also compress surrounding nerves, especially the optic nerve, resulting in a loss of vision.²

Headaches due to prolactinoma are typically located around the forehead and behind the eyes, aligning with the tumour position. They can range from mild discomfort to intense and disabling pain, where the severity is not correlated to tumour size but to prolactin levels. These headaches can be persistent and frequent. They are described to be similar to migraines and cluster headaches.³ Since these headaches are a result of pituitary tumours, they may be accompanied by additional symptoms such as vision loss or hormonal imbalances. Therefore, standard treatments for headache may not be helpful here and may require targeted treatment.

Diagnosis of prolactinoma

To diagnose someone with prolactinoma, a comprehensive medical history of the patient would be recorded to identify symptoms, duration, and associated factors. Specific information regarding headaches characteristics, such as location, intensity, frequency, and response to treatments would be acquired as well.Diagnostic tests for prolactinoma detection include:

• Blood tests: Prolactin levels in blood are measured to confirm that they are indicative of prolactinoma. If levels are high, further testing is carried out, including a comprehensive metabolic panel, thyroid function test (TSH), and a pregnancy test for women. Other hormone levels (cortisol, ACTH, IGF-1, LH, FSH, and sex hormones) are checked to rule out other conditions
• Imaging: An MRI would be performed to visualise the pituitary gland and identify tumour size and location. Alternatively, a less preferred CT scan could be undertaken which is useful to detect larger tumours
• Visual field tests: A visual field test is carried out to assess any impact on the optic nerves, particularly in cases with visual symptoms

Treatment Options 

Dopamine agonists are the primary treatment for prolactinoma. Common drugs include bromocriptine and cabergoline. They work by stimulating dopamine receptors to reduce prolactin production. They also shrink the tumour, by suppressing proliferation of prolactin-secreting cells in the pituitary gland. This mode of treatment should be gradually stopped if prolactin levels are normal and the MRI does not detect the tumour, after a minimum of two years of administration.

A surgical intervention is considered as the preferred option in the cases such as:

• Medical treatment being unsuccessful despite administering maximum dosage
• Potential pregnancy of a woman with a large existing tumour

Transsphenoidal surgery is the common surgery, where the tumour is accessed and removed via the nose instead of the skull.

When surgery and medication are ineffective or not an option, radiation therapy is performed. It can help shrink the tumour and reduce prolactin levels. However, it is typically considered as a last resort due to risks such as potential damage to surrounding brain tissues and long-term hormonal imbalances. 

Mechanism linking prolactinoma to headaches

When a prolactinoma enlarges, it can compress the surrounding tissues, especially around the pituitary. This pressure can lead to headaches and vision loss due to its proximity to the optic nerves.

Large prolactinomas can increase pressure within the brain, causing persistent and often worsening headaches. Nausea, vomiting, and altered mental status may be experienced if the pressure becomes too severe. However, the intensity of pain experienced is not related to the size of the tumour.

Studies found that high prolactin levels can affect neurotransmitter activity, potentially increasing sensitivity to pain and contributing to headaches. Prolactin’s interaction with pain pathways might increase headache frequency and determine intensity. This differentiates prolactinoma-associated headaches from typical headaches.⁴

Managing headaches in prolactinoma patients

Over-the-counter pain relievers or prescription medications can help manage headache pain. In case of severe headaches, especially those with migraine-like features, medications like triptans which are migraine specific may be used. These drugs target the mechanisms causing migraines, offering relief from intense pain.

Implementing lifestyle changes can help prevent other types of headaches that might exacerbate a prolactinoma-induced headache. Managing stress by practicing yoga, meditation and relaxation can alleviate pain and reduce frequency. It is important to maintain regular sleep patterns to prevent headaches triggered by sleep disturbances. Physical therapies such as physiotherapy, which can alleviate tension, and acupuncture, which may reduce pain by stimulating specific points on the body can help handle the headache better. Together, these approaches can improve overall well-being whilst reducing headache occurrences.

Prognosis and long-term management 

Regular follow-up visits are essential to monitor prolactin levels and evaluate the effectiveness of the treatment prescribed. This allows for treatment plans to be altered and adjusted depending on the response of the patient and changes in symptoms. Strategies should be put in place to aid with the management of chronic symptoms, such that quality of life can be maintained. By gaining access to support networks and educational resources patients and families can gain valuable emotional and practical support.

Summary 

Identifying the connection between prolactinoma and headaches is important for timely diagnosis and treatment. The patients' quality of life can be significantly improved by effective management addressing both the tumour and its associated symptoms.

Individuals with persistent headaches are encouraged to consult a medical professional to determine if underlying conditions like prolactinoma are present and receive suitable care.

To maintain overall health and well-being of prolactinoma patients, it is essential that regular health check-ups are carried out and the condition is being proactively managed, addressing both physical and emotional needs of patients.