by NATASHA COURTENAY-SMITH... For the Dailyfemail
Growing pains: Ellie Mae-Holden had treatment to prevent the early onset of puberty
At the age of three, the worries of most little girls rarely stretch beyond what outfit to dress their dolls in, and how to ride a bike.
But for Hayley Smith, her third year brought a set of problems most children her age wouldn't even have heard of, let alone been able to comprehend - puberty.
While her baby-sized friends enjoyed the simplest of life's pleasures, Hayley spent her time laid up on the sofa with period pains.
She also had to put up with other un-pleasantries of puberty, including body odour, greasy hair and mood swings. Not surprisingly, her parents, Debbie, 41, a chemist and David, 45, a project manager from Nottingham, were left both distraught and baffled by the changes in their daughter's body, and behaviour
I first noticed Hayley had body odour shortly after she'd turned three," says Debbie, who also has a 12-year-old son, Carl.
"Around the same time, she suddenly gained a lot of weight, despite not eating any more than she usually did. I thought it was very odd, and I mentioned it to my mother.
"When she told me that you wouldn't expect body odour until a child was approaching their teens, I felt sick with worry. I knew something wasn't right. Then, a few months later, I noticed pubic hair growth, and her breasts were beginning to grow too.
"Hayley was still going to nursery, and didn't seem unwell. All she wanted to do was make cakes and do colouring in. But David and I were very upset, and worried sick.
"Until then, Hayley had been a textbook child, hitting every developmental milestone at exactly the right time. We couldn't work out what was happening to her."
A series of tests with an endocrinologist - a doctor specialising in hormone-related disorders - revealed that Hayley's bone age was advanced, but no firm diagnosis was reached.
Instead, her parents say they were made to feel as though they were over-reacting. However, by the time Hayley was approaching her fourth birthday, it was clear to Debbie that she was on the verge of menstruating.
"Hayley started suffering from terrible stomach cramps and mood swings," says Debbie, who in a bid to raise awareness of the condition is appearing on ITV's Tonight programme this evening.
"She'd lie on the sofa, and tell me she felt tired and miserable. I kept a record of when she was unwell in my diary, and I quickly realised that her symptoms were coming in a regular monthly cycle.
"The thought that my three-year-old girl was getting her period seemed incomprehensible, but at the same time, it was becoming obvious to me that her mood swings and stomach cramps were to do with her time of the month.
"The endocrinologist may have dismissed my worries, but I could just tell that my daughter was entering puberty."
And Debbie's instincts proved to be correct. After numerous examinations and tests over the following 18 months, Hayley, at age six, was finally diagnosed with precocious puberty, a condition in which puberty begins at an unusually early age often due to abnormal production of oestrogen, thought to affect as many as one in six children under ten.
Although her periods didn't start until she was eight, her monthly cycle of stomach cramps and bad moods had been a warning sign that her ovaries were maturing, and were a sign of the fluctuating hormones that define puberty.
Her breasts also grew and Hayley, now aged 12, wears a C cup bra.
"Hayley has always taken it all in her stride," says Debbie. "I thought for instance that she'd be upset when at five she had to start using deodorant. But she didn't say to anything to me about being different to other children, and she didn't seem to be confused either.
"Instead, she told me she 'liked being like Mummy'. I bought her a book called My Changing Body, which I used to read to her at night time to help her understand what was happening to her, and she didn't seem frightened or scared by any of it.
"I meanwhile, was extremely confused as to how it was possible that a child who was only just forming sentences and learning to read and write was developing the body of a growing adult.
"And it did get to her when she was the only girl sitting on the side of the pool in swimming lessons because of her periods. She felt very left out. As a result of the hormone imbalances in her body, the condition has made her overweight and unusually tall for her age, which has meant she has endured some bullying too.
"Things are getting better now that the other girls are catching up with her, but Hayley still struggles to control her weight.
"And I still have sleepless nights about it. Although I've been reassured the condition won't affect her future fertility, I find it hard to see how it could have no impact at all."
And Hayley is far from alone. Over the past century, the normal age at which puberty starts in both boys and girls has dropped by about two years.
In fact, a recent study showed that British girls today start their periods at an average age of ten years and three months, compared to 11 years nine months for their mothers and 12 years for their grandmothers.
But for a small group of children - there are no official figures - puberty is coming even earlier.
The condition is more common in girls, but in young boys, precocious puberty causes rapid growth spurts, acne, the growth of facial and pubic hair and a deepening of the voice.
"In most cases, puberty would be considered precocious if it started in a girl aged eight to ten and a little later for boys," says Tam Fry, spokesperson for the Child Growth Foundation. "But some of the children we have been dealing with have been displaying signs of puberty as early as three years old.
"It is a tremendously concerning condition - both for the parents and for the children in question.
"There are a number of girls who have been left seriously traumatised by going through puberty at a stage where, mentally, they are not equipped to cope with it. And it's very hard to cope in daily life if you're an eight-year-old girl who looks like a mature woman."
Certainly, that was the experience of Lucia Reed, now 20, who started having periods at the age of six. A graphic design student from West London, Lucia has haunting memories of receiving sexual attention from grown men at a very young age.
"The hardest thing of all about precocious puberty was that men would come on to me as though I was an adult. "I remember walking home from school aged eight, and I'd often get followed by men leering at my body. I was still in primary school and had no idea what was happening. I used to have to phone my mother and get her to come and pick me up. It was really frightening."
Though she is now able to speak candidly about going through puberty so early, it is clear that even if a child puts on a brave face, life can be very difficult. Lucia says precocious puberty left her isolated from her peers, and lead to frequent medical examinations which terrified her.
"I don't remember being told I had precocious puberty as such, or even the day my periods started," says Lucia. "All I remember is feeling completely alone and alienated as a child. I was overweight, much taller than everyone else - at one point I grew an inch a month - and I stood out like a sore thumb. At the age of seven, I had the bone age of a 14-year-old and was almost five foot tall.
"But it wasn't just my height. My breasts developed too - I had to wear a bra from the age of eight, and the other children teased me relentlessly. I also had to cope with terrible acne, greasy hair and huge mood swings.
"I ended up feeling very self-conscious and really uncomfortable in my body. I suffered from terrible growing pains too, and I was far too embarrassed to tell my peers about my periods, which left me feeling as though I was carrying a horrible secret around with me."
Even at secondary school - by which point her peers had started to catch up - Lucia still felt like an outsider.
"I was still larger than the other girls, so I ended up taking on the role of mother hen," she says. "My peers were beginning to come to me for advice, which helped me feel a bit better about myself.
"But even so, I still knew I was different, and I just wanted to be like everyone else. I think of childhood and my teens as very lonely times indeed."
While some parents - such as Debbie, and Lucia's parents - chose to let nature take its course and allow puberty to continue, others opt to give their child treatment, which involves suppressing the secretions of hormones which initiate puberty with a range of drugs and injections.
With treatment, actual puberty can be staved off until the child reaches a more appropriate age.
That was the decision taken by Hayley Holden, 31, a full-time mum from Padstow, Cornwall, when she discovered her daughter Ellie Mae, then just three, was on the verge of starting her periods.
Hayley had taken Ellie Mae to the doctor, concerned she was developing breasts. Her GP spotted the signs of precocious puberty immediately.
"I'd never even heard of precocious puberty, and although I was concerned enough about Ellie Mae to take her to a doctor, I actually thought I was imagining things," says Hayley, who is separated from Ellie Mae's father and has three other children, twins Charlie and Chloe, 11, and Albie, 4.
"But a bone density test revealed that at just three, Ellie Mae had the bone age of a nine-year-old, and I was told that if we didn't intervene with medication, she was just six months away from starting her periods. I was in bits when we got the news. I just had no idea what to think about it."
"I felt that full-blown puberty at the age of four would be too much for Ellie Mae to cope with,' says Hayley.