For a year, Derin Gebhardt and his wife, Sandra, tried every took and trick in the book to have a baby, religiously using a basal body thermometer to track ovulation and keeping an eagle-eye on Sandra's menstrual cycle - but with no luck.
Meanwhile, Derin's physique was changing, inexplicably.
He was a volunteer firefighter, and devout to eating only his home-cooked meals, yet Derin's active, nutritious lifestyle was doing nothing to stop him from gaining weight.
A trip to the family doctor in the couple's hometown of Roundup, Montana, in early 2017, revealed that Derin's testosterone levels were low.
There were a few possible explanations, but biomarkers in Derin's blood pointed toward one that confounded the couple: a brain tumor.
One week later, the Gebhardts learned that Derin, 37, had a benign mass, called a pituitary tumor, in his brain.
The pituitary gland is crucial to the body's regulation of testosterone and semen production, and the tumor was interfering with the hormones the gland produced, resulting in Derin's fertility and weight issues.
The couple sought treatment at the Mayo Clinic in Phoenix, Arizona, where doctors first prescribed Derin medication to shrink the tumor, and then performed surgery to remove it.
Six months into treatment, Sandra became pregnant and, in June 2018, their son, Gage, was born.
Gage will be turning one year old this month and the couple tells DailyMail.com that they never Derin would need to undergo brain surgery in order for them to have a child.
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Derin Gebhardt, 37, from Roundup, Montana, and his wife, Sandra, 38, tried getting pregnant for a year between 2016 and 2017 with no luck. Pictured: Derin (right) with Sandra and their son, Gage
After undergoing tests at their family doctor, Derin discovered that his testosterone levels were low and that he might have a tumor. Pictured: Derin with Gage
In March 2017, Derin was diagnosed with a pituitary tumor, a benign tumor that grows on the pituitary gland in the brain. Picture: Scan of Derin's brain
Sandra told DailyMail.com that she first saw Derin online, during a Facebook campaign set up by his friends to get him on NBC's The Biggest Loser in 2010.
He wasn't cast in the show but, months later, Sandra learned they had mutual friends.
'He popped up in a picture [on Facebook] with one of my nephew's moms,' Sandra, 38, said.
'She was trying to set me up with somebody - and it turns out it was him - and I was like: "I know who he is. I have a bit of a cyber crush on him".'
The couple immediately began dating and married in March 2014.
After they got married, Sandra noticed that Devin was still putting on weight despite eating home-cooked food and living an active lifestyle.
'I was doing all the cooking and he was active,' she said. 'I said: "It doesn't make sense why you keep getting weight." I think at his heaviest, he was 460 [pounds].'
Visits to several doctors confirmed that Devin had high cholesterol and high blood pressure, and was pre-diabetic, but not what was behind these conditions.
The tumor was inhibiting Derin's testosterone and semen production, and was also behind his weight gain. Pictured: Derin and Gage at the Roundup Volunteer fire station
During this time, Sandra and Devin were also trying for a baby. For about a year they tried, unsuccessfully.
'I had the thermometer [to check my ovulation], charts, all the research from websites,' Sandra said.
'It was definitely frustrating. There was a lot of frustration and humiliation, and Derin was as down as I've ever seen him.'
Derin said the struggle to conceive spun him into a depression-like state.
'There's obvious frustrations when your body doesn't work the way it's supposed to,' he told DailyMail.com. 'I figured that it was all a product of the way I had been living.'
The couple seemed, at one point, resigned to the fact that they would never have a biological child and started discussing adoption.
'There were talks about whether we would adopt an infant or an older kid who needed a home,' Sandra said.
During a routine visit to his family doctors, the Gebhardts had Derin's testosterone levels checked and found they were quite low.
'The doctor said he didn't know they could even go that low,' Sandra said.
Derin had a blood test performed, and the doctor delivered some shocking news: there was a chance Derin had a tumor, but the blood work need to be sent off to confirm the results.
One week later, while the couple was on vacation with friends in Mexico in March 2017, they learned that Derin had a pituitary tumor.
Pituitary tumors are benign tumors that grow in the pituitary
