Research led by Ragner Liedman of the University of Lund in Sweden has uncovered a possible role for oxytocin in dysmenorrhoea, commonly known as menstrual cramps.

The researchers took biopsies at the time of ovulation from the endometria of normally menstruating women and those who experienced cramps. They looked at gene expression for the receptors for oxytocin, vasopressin (a related peptide), estrogen and progesterone.  And they found a difference in the oxytocin receptors in the women experiencing painful periods.
Here's the nut graph of the study abstract:

The gene expression for oxytocin receptor was significantly lower in dysmenorrhoic than in healthy women, in median 1.21 and 3.44 oxytocin-receptor/actin, respectively (p = 0.048). The expressions for oxytocin peptide, vasopressin V1a receptor, oestrogen receptor α, β and progesterone receptor did not differ between the two groups. Expression of vasopressin peptide was not detectable.

It's important to note that they were not looking at oxytocin levels. Receptors are cellular structures that allow a cell to take in a specific chemical. So, if you have fewer of them in an area, that area won't be able to use as much of a chemical, even if it's circulating through the body.

The other thing to note is that the number, distribution and sensitivity of these receptors seem to vary. You could think if them as algae blooms: the algae are always in the water, but sometimes external conditions make them suddenly proliferate. We're born with the genes to create oxytocin receptors; but external circumstances, from the cellular level out to beyond the skin, "turn on" or "off" these genes. When a gene is turned on, it's known as gene expression.

The first stimulus to expression of the oxytocin gene seems to be immediately after birth. In rats, the mother's licking and grooming of her babies causes oxytocin receptors to proliferate. Babies that don't get as much grooming develop fewer oxytocin receptors.

Oxytocin receptors in the uterus also proliferate during pregnancy and especially right before childbirth.

So, I wonder if there might be a link between very early experiences of nurturing as a baby and later menstrual cramps.

I also wonder if oxytocin might be a good remedy for dysmenorrhoea. Kerstin Uvnas Moberg, a Swedish researcher and author of "The Oxytocin Factor," found that an oxytocin gel applied to the vulva was an excellent remedy for symptoms of menopause, including vaginal dryness and hot flashes. She was trying to form a company and begin marketing this, but ran into some difficulties. Dysmenorrhoea could be another area for her.

Two of the researchers on the team are with Pfizer Global Research, so maybe they're also thinking about this.

Meanwhile, I can think of a good home remedy for cramps: have terrific sex by yourself or with someone else. Of course, that's about the last thing most of us feel like doing at that time.