Prolactinoma And Vision Problems

Introduction

Prolactinoma is one of the most common types of pituitary tumour and is located in the base of the brain, which secretes excessive amounts of a hormone called Prolactin which has the main function of signaling women’s breasts to produce milk during pregnancy and breastfeeding. 

This tumour can have many effects, depending on its size and location. Its location near the nerves of the eyes can cause serious vision problems, including reduced peripheral vision or blindness.

Prolactinoma causes and symptoms 

The cause of Prolactinoma is still unknown, however, many factors can play a role; these include

• Inherited disorder Multiple Endocrine Neoplasia type 1 which increases the risk of developing prolactinoma
• Certain medications including antipsychotics, antiemetics, antihypertensives, and opioid analgesics
• Some illnesses; kidney disease, hypothyroidism, shingles, cranial irradiation, sarcoidosis, and empty sella syndrome. 

There are some causes in which prolactin levels increase temporarily and go back to normal after a certain time;

• Pregnancy
• Breastfeeding
• Exercise 
• Sexual activity
• Trauma to the chest area
• Epileptic fits.

Symptoms of prolactinoma differ depending on the size, location and sex of the person.

Among women, common symptoms include

• Irregularity of periods
• Difficulty to conceive
• Milky discharge from the breast
• Loss of libido

Among men, common symptoms include

• Loss of libido
• Erectile dysfunction
• Impotence

Among children and adolescents, common symptoms include

• Growth arrest
• Primary amenorrhoea
• Delay in puberty

Diagnosis of a prolactinoma 

Diagnosis typically involves a set of blood tests. The most important one is the serum prolactin levels which indicate the level of prolactin in the blood. Assessment of other pituitary hormones is also done including TSH, ACTH, LH, FSH, IGF-1, and testosterone/estradiol. 

Blood tests are followed by imaging tests to confirm the size and location of the tumour. MRI is the preferred choice to locate the prolactinoma over a CT scan.

Vision problems associated with prolactinoma  

Patients with small pituitary tumours do not typically develop visual symptoms. However, if a pituitary tumour is bigger which means more than 1 cm, a patient can exhibit visual symptoms in one or both eyes. One pattern of visual loss that characteristically occurs is reduced peripheral vision to both sides. However, these changes can be difficult to notice by the patient.

The pituitary gland is situated within a small pocket known as the pituitary sella, positioned just a short distance behind the eyes. Our ability to see relies on the transmission of visual information from the eyes to the brain through a network of fibres called optic nerves.

However, when a large pituitary tumour develops, it can put pressure on these optic nerves, disrupting their ability to relay visual signals from the eyes. In some cases, the tumour may specifically impact one optic nerve, leading to visual impairment in a single eye. 

Alternatively, it may affect the optic chiasm, a structure where the optic nerves from both eyes converge. When the tumour compresses the optic chiasm, it results in bitemporal hemianopia.

Beyond the optic nerve, which serves as the pathway for visual information, several other nerves near the pituitary gland play a role in controlling eye movement. If a pituitary tumour presses against one of these nerves, it can weaken the muscles responsible for moving the eyes. 

Consequently, this muscle weakness disrupts the normal alignment of the eyes, resulting in a condition known as double vision, where the eyes fail to focus on the same point, causing two overlapping images.

Diagnosis of vision problems in prolactinoma patients

Diagnosing vision problems in prolactinoma patients requires a multidisciplinary approach involving endocrinologists, neurosurgeons, and ophthalmologists. 

Clinical assessment typically includes a detailed medical history, examination, and assessment of visual acuity, colour vision, and peripheral vision. 

Ophthalmological evaluation may involve visual field testing, fundoscopy, and optical coherence tomography (OCT).

Imaging studies, including MRI and CT scans, are essential for visualizing the pituitary gland and assessing the extent of tumour growth and its proximity to critical structures such as the optic nerves and chiasm. Early detection and prompt treatment of vision problems are crucial to prevent permanent visual impairment in prolactinoma patients

Management and treatment

Treatment options may include medical therapy to alleviate the symptoms and shrink tumour size. This includes dopamine agonists. 

Then there are surgical options that aim to debulk the tumour and partially excise it to reduce the mass effects on the nerves and relieve the visual symptoms. Surgical excision has shown better results compared to other modalities. 

Recurrence is always a possibility in tumors that are partially excised, hence follow-up is crucial after 2-3 months after treatment and at 6-12 month intervals depending on the course of treatment.

Complications

Some complications may occur while treating prolactinoma, which are:

1. Pituitary apoplexy –a life-threatening emergency that involves infarction or haemorrhage of the pituitary gland
2. Tumor recurrence
3. Secondary empty sella syndrome; after surgical removal of the pituitary gland, the sella remains empty and sometimes the optic chiasm herniates into this space causing secondary visual loss. 

Prognosis 

The prognosis after treating pituitary adenomas depends on various factors such as the patient's initial visual condition, age, duration of symptoms, the severity of visual impairments, presence of optic nerve damage, and tumour size. Recovery typically occurs within a timeframe that can range from months to years after the course of treatment. 

Early visual recovery, often observed within the first 24 hours post-surgery or 24 to 72 hours after beginning medical therapy, signals a positive response to treatment. However, the most significant improvements typically occur within the first four months post-treatment, with ongoing progress observed up to three years in some cases.

Surgical excision of the tumour mostly leads to improvement in visual acuity and visual field defects in most patients. Conversely, individuals undergoing radiation therapy may experience a slower pace of recovery and delayed improvement compared to those treated surgically.

Summary 

In conclusion, prolactinoma can have significant implications for vision health, leading to various ocular symptoms and visual disturbances. Early recognition of vision problems in prolactinoma patients is critical for timely intervention and preservation of vision. 

A multidisciplinary approach involving endocrinologists, neurosurgeons, and ophthalmologists is essential for the comprehensive management of prolactinoma and its associated vision problems.

Continued research efforts are needed to further our understanding of the pathophysiology of vision impairment in prolactinoma and to improve treatment outcomes for affected individuals.

FAQs

What is a pituitary adenoma?

• It is a benign pituitary gland tumour, located at the base of the brain. It is responsible for secreting hormones that signal our endocrine glands in the body. 

What are the symptoms of a pituitary adenoma?

• Symptoms can vary depending on the size and location of the tumour but may include headaches, vision problems, hormonal imbalances, such as changes in menstruation or libido, and symptoms related to pressure on nearby structures in the brain

How common are pituitary adenomas?

• Pituitary adenomas are relatively common, with studies suggesting they account for up to 10-15% of all intracranial tumours. They are often discovered incidentally on imaging studies performed for unrelated reasons

Are pituitary adenomas cancerous?

• No, they are almost always benign (non-cancerous). However, they can cause significant health issues due to their size and location.

Are there support groups available for individuals with pituitary adenomas?

• Yes, there are many support groups and online communities dedicated to providing information and support for individuals with pituitary adenomas and their families. These groups can offer valuable support, resources, advice, and encouragement to those affected by this condition.