By Jane Elliott
BBC News health reporter
Millions of women around the world have reason to be grateful to GP Dr Katharina Dalton, yet few have even heard her name.
Dr Dalton's (second left) testimony was often used in court
Dr Dalton, who died last year, was the GP who first discovered premenstrual syndrome (PMS) over 50 years ago.
She provided a much-needed explanation for the monthly periods of ill health which affect so many women.
And they swore by the treatments she offered at the clinic she set up and ran for 40 years.
She first became fascinated by the menstrual cycle while pregnant when she noticed the migraines that normally plagued her each month were absent.
In her first month as GP, she was called to the house of an asthmatic exhibiting severe breathing difficulties.
The woman's husband informed her the same thing happened each month.
Intrigued, Dr Dalton then started to keep a note on those female patients who visited her at regular times each month.
She soon concluded that PMS and postnatal syndrome were caused by a lack of the hormone, progesterone.
After a series of studies, she decided to treat it with diet and large doses of the hormone.
Her patients' experiences suggested this worked.
She also carried out research at Holloway women's prison.
Here she found that 49% of the newly convicted prisoners that she interviewed had been sentenced for crimes committed during the four days prior to the start of a period and the first four days of it - known as the paramenstruum.
Chris Ryan, National Association for Premenstrual Syndrome (NAPS) Chief Executive, said Dr Dalton's expertise was often called upon in court cases.
"Her testimony was frequently sought to defend women who pleaded diminished responsibility because of premenstrual syndrome.
"She was an expert witness for the defence of Anna Reynolds, a woman charged with manslaughter, and of Nicola Owen, an arsonist who struck at intervals that were multiples of 28 days.
"Both women were acquitted."
Dr Dalton also carried out work on migraine and its link to diet, the effect of progesterone on the foetus, pre-eclampsia and postnatal depression.
Yet despite all her innovative work, her supporters feel that her legacy to the world of women's health was largely unnoticed.
This week NAPS, which she helped establish in 1983, honoured her memory with a memorial lecture.
Mr Nicholas Panay, Consultant in Obstetrics and Gynaecology at Queen Charlotte's and Chelsea Hospital London, who delivered the lecture said Dr Dalton had earned her place in the medical history books.
"Dr Dalton was an undisputed pioneer in our understanding women's reproductive health.
'Behind the curtain'
"She was the first to give clinical definition to the cyclical psychological and physical symptoms experienced premenstrually by millions of women.
"Many in the medical establishment at the time, and even today would not accept her work. Yet Dr Dalton is hailed by women worldwide for providing the clinical explanation of their recurrent cyclical ill health and a treatment pathway.
"This lecture will place her legacy into its proper context and encourages a full acknowledgement of her place in the history of women's health."
Mr Ryan agreed she was a pivotal figure in women's health: "She did such a lot for women. She gave them the confidence to acknowledge that their menstrual cycle was an important factor in their health.
"She brought PMS from behind the curtain and by doing so she did a hell of a lot of good."