He specialized in obstetrics and gynaecology, and contributed significant research to the field of women's health, in particular about menopause and hormone replacement therapy.
[2] In his early research, Judd and his collaborators showed that the ovaries of postmenopausal women could secrete amounts of androgen, which can act as precursors to estrogen.
He developed techniques to monitor the onset and severity of hot flushes, using electrodes to measure rises in skin temperature due to vasodilation, and pulse rate.
[1] These objective measurements of hot flushes later assisted in assessing the effectiveness of treatments mitigating the signs and symptoms of menopause, including hormone replacement therapy.
The trial was halted in 2002 following results showing that women on hormone replacement therapy were at a higher risk of developing cardiovascular disease and breast cancer.