SINGAPORE - When Jeremy Cheong, 41, attended his secondary school reunion party in 2024, he said his former classmates looked their age - with wrinkles on their faces and frown lines between their eyebrows.

Standing among them, the administrative executive looked like a young man in his 20s. He could even have easily passed off as one of their sons.

"Nobody really explained to me that because my cortisol production had stopped, I had to be on steroids for life. The good thing is that I won't age. It actually took me 10 years to realise it," Cheong told The Straits Times.

Cheong looks forever young due to a rare condition called panhypopituitarism.

The condition is caused by the reduced production of hormones in the pituitary gland, a pea-size organ that sits behind the bridge of the nose at the base of the brain.

"The gland controls many of our hormonal functions, like our thyroid gland, the maturation of our sexual organs in both gender, production of growth hormones, the regulation of human output from our body," said Dr Mok Shao Feng, a senior consultant in the Division of Endocrinology at the National University Hospital. 

The pituitary hormones are in charge of several important functions in the body, such as metabolism, growth and reproduction.

There are about four cases of panhypopituitarism per 100,000 people worldwide a year.

Dr Mok said that "patients can be diagnosed with varying symptoms and at different stages of their life".

"In individuals who have young onset of the disease can have delayed puberty, missing the pubertal milestones. For female patients, they can present with missed or irregular periods, sub fertility, and difficulty in conceiving... When it comes down to the other hormones, the general symptoms include feeling more tired and putting on weight," he said.

Dr Mok added that in some patients, like Cheong, many hormonal functions are affected,

The endocrinologist said the most common cause of panhypopituitarism is tumours in the hypothalamus or pituitary gland.

"Even though they are benign, they are growing in an enclosed space, causing problems such as compression. Patients lose vision, particularly at the peripheral, before it gets worse. These tumours can have propensity to suddenly bleed as well, so that relates to the underlying problem," he said.

"For hormonal deficiency, it depends on how many hormonal axes are affected and whether it is a complete or partial one. Patients with a single affected hormonal axis can go undiscovered for quite a long time. ... You can have the more drastic ones where the symptoms present much earlier. Not only do (these patients) lack the sexual hormone and cannot have puberty, but also the lack of the steroid hormone cortisol, which is important for survival," he added.

Cortisol, or the stress hormone, is responsible for maintaining constant blood pressure and blood glucose levels, regulating immune function and anti-inflammatory mechanisms, and it dictates the fight-or-flight response. The lack of cortisol can be associated with a younger looking appearance.

Cheong was diagnosed only at the age of 21. He still looked like a boy in his mid-teens then.

"That year, I realised I was getting fatter. I also realised I was heat intolerant... The first thing I did was see an endocrinologist and was given a blood test. That was when I found out that I had hypothyroidism. I was also told if I continued being in this state (without treatment), I would have died," he said.

Cheong added that scans showed that his condition was caused by a tumour near his hypothalamus. In 2005, he had both the tumour and his hypothalamus removed, he told ST.

Once the hypothalamus is damaged or removed, dysfunctions can manifest in various areas. These include body temperature, growth, weight gain, emotional control, sleep cycle, and a deficiency of the antidiuretic hormone (ADH), resulting in frequent urination and thirst.

"I had trouble sleeping over the next 10 years until 2015 when I was given medication to deal with my sleeplessness," Cheong said.

Currently, he is still on a battery of medication, including an ADH, to help him manage the symptoms caused by the condition.

While most people in their 40s try to look younger, Cheong tries his best to look much older. He said one trick was to try to have a lot of facial hair. He told ST that he managed to grow a goatee once.

"When I look back at my 20s and my 30s, I looked really young then," he said.

"The joke here was whenever I tell doctors that I have panhypopituitarism, they, especially the women, would wish they have it too," he added, laughing.

And whenever he was in public places such as the mall or hawker centre, older women would call him "ah boy".

"I guess at my age now, it is actually nice to be called 'ah boy'," Cheong said.

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This article was first published in The Straits Times. Permission required for reproduction.