A man in the U.K. had to drink 10 liters of water every day for two years to quench his "constant thirst." Jonathan Plummer, 41, initially thought his increased thirst and fatigue were due to diabetes until he took an eye test.

"I felt a constant thirst that I couldn't quench and got to the point where I was passing as much water as I was drinking. It was an awful time which caused me to miss days of work at a time and I experienced extreme fatigue," Plummer told Birmingham Live.

Although Plummer had the most common symptoms of high blood sugar, including increased thirst, fatigue and frequent urination, his tests were not conclusive of diabetes.

However, during a routine eye test, doctors found a mass and directed Plummer to undergo an MRI screening. He was diagnosed with a type of brain tumor – a germ cell tumor on his pituitary gland that interfered with water retention.

"I was devastated. The tumor was growing on my pituitary gland — which was causing my need to drink water all the time — and many other 'spots' on my brain," he said.

Plummer was placed on steroids to reduce the pressure of the tumor on the brain. After around 30 rounds of intense radiotherapy, the man is now cancer free but has to be on lifelong medication. He now raises awareness about brain tumors.

"I have suffered from the devastating effects of brain tumors but was one of the fortunate very few to survive but still live with the effects, brain tumors kill more children and adults under 40 than any other cancer and just 12% survive beyond five years," Plummer, who is raising money for Brain Tumor Research, wrote on the fundraising page.

What are pituitary tumors?

A pituitary tumor is an abnormal growth in the pituitary gland located at the base of the brain that regulates the hormonal balance of the body. Most pituitary tumors do not have symptoms. The symptoms also vary depending on the type of tumor and the affected area of the pituitary gland.

Here are some of the common symptoms associated with pituitary tumors:

  • Hyperthyroidism - when the tumor affects the thyroid production
  • Cushing syndrome - when the tumor raises cortisol in the blood
  • Gigantism or slow growth - when growth hormone gets affected
  • Headache
  • Eye problems - loss of peripheral vision or double vision.
  • Pain in the face
  • Drooping eyelid
  • Seizures
  • Nausea and vomiting
  • Fatigue
  • Nipple discharge, irregular or absent menstrual periods in women
  • Decreased sexual function in men

When the tumor grows, it can cause damage to the pituitary gland, causing hormonal imbalances that leads to excessive thirst, urination and slow growth.