It's no secret that the men in Britain's Royal Family are prone to Male Pattern Baldness.
Both the brothers have joked about their thinning hair over the years, with Prince William's starting from around 23 years of age. The elder brother and father of three now has extensive baldness in all the areas which can be affected by this hereditary condition - along the top of the scalp, from hairline to crown - which he wears well.
Harry seemed to start showing signs of hair loss a little later in life than William. A drop in the volume of his traditionally thick ginger hair became noticeable when he was around 28 years old, followed by general thinning, particularly at the crown.
Since pictures of his rapidly growing thinning crown were published in November 2018, many media outlets have been reporting on how quickly Prince Harry, Duke of Sussex, has been losing his hair since marrying Meghan Markle in May 2018. The following photos of the Duke and Duchess of Sussex are from 2nd February 2019. Continues below...
Here we look at a number of possible reasons that could account for, or be contributing to, the Prince's rapid hair loss.
One of the key influencing factors when it comes to accelerating the rate of shedding in cases of Male Pattern Hair Loss is stress. This can be emotional stress as well as physical strain, such as that caused to the body when there is an underlying or additional health issue such as an illness or nutritional deficiency.
Whilst stress in itself can lead to thinning hair and exacerbate genetic balding, it can also lead to increased bad habits which can have further negative effects on the hair. Smoking has established links to hair loss, making hair dry, thin and also potentially turning it prematurely grey.
Prince Harry was a smoker but is believed to have given up before his wedding. As any former smoker knows, though, stressful times can make it easy to slip back into this unhealthy habit.
The numerous Markle family dramas, as played out in the British and American tabloid press, a rumoured rift with his brother William, and the way mixed-race Meghan has been treated by some sections of the UK media, have been cited by many correspondents as causes of intense concern for the newly-married Royal.
Add in the pressure of being part of one of the world's most well-known families, his international schedule of royal duties and charity work, as well as the anxiety of being an expectant family, and it's easy to see why Harry may be experiencing stress-related hair loss.
Harry is understood to have made a number of positive lifestyle changes both since meeting Meghan Markle and to support her during her pregnancy. These include giving up drinking, less caffeine, eating better with more fruit and vegetables and less meat, as well as exercising regularly and trying out yoga for relaxation.
As long as his new lifestyle changes are moderate and sensible, they are unlikely to have any effect on his hairloss - and certainly not any negative ones.
All of these are highly laudable efforts and should, in theory, help the Duke to maintain a generally healthy lifestyle. Where things may become problematic is if Harry throws himself into things too hard - as he did in his partying days.
Any extremes, particularly over a significant period of time - such as frequently over-exercising, severely restricting calories or nutrients, or anything which causes rapid weight loss - can reflect in the hair. As the body reacts to any sudden changes by diverting its resources away from non-critical functions, such as hair growth, to ensure the critical organs are protected, hair follicles can suffer. In these instances temporary hair loss often ensues, making Male Pattern Baldness worse for at least six months.
Another theory is that that the Prince may have stopped using hair loss treatment in order to start a family; Meghan and Harry are expecting their first child in April 2019.
If Prince Harry had been taking finasteride 1mg - one of only two MHRA-licensed and FDA-approved male pattern hair loss treatments - he would have had to stop taking this around one week in advance of trying for a baby.
Once hair loss treatment is ceased, the regained hair will start to shed again within around three to six months, then continue to thin. Harry and Meghan married in May 2018, so, if he stopped using treatment after the wedding, the 34 year old could expect his hair loss to become noticeable again by November of that year - the month the photos of his increased hair thinning were published in the media.
Although he has allegedly dallied with different hair loss solutions, from something thought to be high strength minoxidil, to food supplements for hair growth, in the past, whether or not Harry has ever tried used a clinically-proven pharmaceutical approach to his thinning hair remains unconfirmed.
It was previously noted by Royal watchers that Prince Harry's hair had been looking fuller than usual on and in the run up to his Wedding Day, however, this could have been down to cosmetic products, such as microscopic fibre concealers.
Whatever the reason for the ups and downs of Harry's hair, how he chooses to deal with going bald is his own personal decision - just as it is for all men affected by this common condition - and we're sure he will have plenty of advice for where to turn, should he require the advice of dedicated hair loss specialists on the available options.
The Belgravia Centre is a world-renowned group of a hair loss clinic in Central London, UK. If you are worried about hair loss you can arrange a free consultation with a hair loss expert or complete our Online Consultation from anywhere in the world for home-use treatment.
View our Hair Loss Success Stories, which includes the world's largest gallery of hair growth photos and demonstrates the level of success that so many of Belgravia's patients achieve.