A rapid and accurate blood test has been developed that can measure melatonin in the blood in extremely small amounts. The method could open new possibilities, including sleep disorders, mental disorders and metabolic disorders. But the researchers emphasise that the clinical work has only just begun.
Millions of people worldwide take melatonin to help them sleep better because it has a central role in the circadian rhythm. Its use has risen markedly among children, adolescents and adults in recent years. Nevertheless, doctors have not routinely been able to measure melatonin in the blood in clinical practice. A new study is now changing this.
At Bispebjerg and Frederiksberg Hospital in Denmark, researchers have developed a rapid method that can measure melatonin in the blood with high precision using just 50 microlitres of blood – equivalent to a small drop from a fingertip.
The long-term ambition is to measure melatonin to diagnose disease, monitor treatment and understand how the body’s biological clock is linked to health. But first, it has to be measured reliably and precisely.
“It would be completely absurd if you had diabetes and started treatment with something designed to lower your blood glucose without being able to measure it. That is similar to the paradox we have faced with melatonin. Many people take the hormone, and many research groups work with it, but in clinical practice we have not been able to measure it. We are now changing that,” says Nicolai J. Wewer Albrechtsen, senior researcher, clinical professor and consultant from the Department of Clinical Biochemistry at Bispebjerg and Frederiksberg Hospital and the University of Copenhagen, Denmark.
The research has been published in the Scandinavian Journal of Clinical and Laboratory Investigation.
An ultrasensitive “bathroom scale” finds the sleep hormone
The new method uses liquid chromatography combined with mass spectrometry (LC-MS/MS). In this process, melatonin is first extracted from blood plasma and then measured using a mass spectrometer – a kind of extremely precise bathroom scale that can determine both what a substance is and how much of it is present.
The method can measure as little as five nanograms of melatonin per litre of blood, and the analysis takes around seven minutes per sample. In addition, the measurements follow the circadian rhythm expected in healthy people.
According to lead author Jakob Albrechtsen, a chemist at Bispebjerg Hospital, this high precision is important because melatonin is only present in the blood in very small amounts. Further, the blood is filled with molecules that chemically resemble melatonin.
“A mass spectrometer is a bit like an extremely sensitive bathroom scale. It can both measure how much melatonin is present and confirm that it is actually melatonin and not some other substance. That kind of precision is crucial for translating research into clinical laboratory knowledge,” he explains.
Blood samples revealed the body’s internal night
To test whether the method actually captured the body’s biological circadian rhythm, the researchers used blood from a previous study in which 24 healthy men aged between 20 and 40 years spent a full 24 hours in hospital under tightly controlled conditions.
The participants were given regular meals, 15 hours of daylight and nine hours in darkness. In addition, blood samples were taken every three hours around the clock, and the participants abstained from alcohol, tobacco, sweets and strenuous exercise.
The measurements closely resembled results from far more labour-intensive methods that have been used for decades. Further, the melatonin levels followed the circadian pattern expected in healthy people.
Melatonin levels were lowest in the afternoon around 15:00, at approximately 12 nanograms per litre of blood. The levels then rose throughout the evening and peaked in the middle of the night around 3:00 at approximately 46 nanograms per litre.
“It is very important that a new method can both measure the hormone accurately and at the same time reveal the pattern we recognise from the literature. Our method has been able to do that,” says Jakob Albrechtsen.
Now begins the search for what melatonin can reveal about disease
Bispebjerg and Frederiksberg Hospital now has the first laboratory in Denmark to offer routine measurement of melatonin in the blood. The department has already received enquiries from both researchers and clinicians.
Melatonin is best known as the body’s sleep hormone, but the hormone has also been linked to stress, mental disorders, metabolic diseases and cancer. That is why there is strong interest in being able to measure melatonin more precisely.
Nicolai Albrechtsen emphasises that the method cannot yet stand alone as a clinical marker. But it could become an important prerequisite for investigating where melatonin measurements may be useful in patient care.
“We are a laboratory, and the next step is to work together with colleagues who are experts in these disease areas. Now the work begins to find out what the sleep hormone can actually tell us. This could be for patients who are already being treated with the hormone and for patients where measurement might provide completely new understanding of the body’s biological rhythms and their importance in disease. It is only now that the real work begins,” he concludes.
