Validation of a test model of induced dysmenorrhea

The Establishment of a Mouse Model of Recurrent Primary Dysmenorrhea

Primary dysmenorrhea is one of the most common reasons for gynecologic visits, but due to the lack of suitable animal models, the pathologic mechanisms and related drug development are limited. Herein, we establish a new mouse model which can mimic the periodic occurrence of primary dysmenorrhea to solve this problem. Non-pregnant female mice were pretreated with estradiol benzoate for 3 consecutive days. After that, mice were injected with oxytocin to simulate menstrual pain on the 4th, 8th, 12th, and 16th days (four estrus cycles). Assessment of the cumulative writhing score, uterine tissue morphology, and uterine artery blood flow and biochemical analysis were performed at each time point. Oxytocin injection induced an equally severe writhing reaction and increased PGF_2α accompanied with upregulated expression of COX-2 on the 4th and 8th days. In addition, decreased uterine artery blood flow but increased resistive index (RI) and pulsatility index (PI) were also observed. Furthermore, the metabolomics analysis results indicated that arachidonic acid metabolism; linoleic acid metabolism; glycerophospholipid metabolism; valine, leucine, and isoleucine biosynthesis; alpha-linolenic acid metabolism; and biosynthesis of unsaturated fatty acids might play important roles in the recurrence of primary dysmenorrhea. This new mouse model is able to mimic the clinical characteristics of primary dysmenorrhea for up to two estrous cycles.

A cohort study of dysmenorrhea and risk of low birth weight

OBJECTIVE

Little is known about the association between maternal history of dysmenorrhea and perinatal outcomes. The aim of this study was to investigate the association between maternal history of dysmenorrhea and low birth weight (LBW).

METHODS

A total of 6754 pregnant women were recruited from the ongoing prospective cohort study in Guangxi, China, in 2015-2018. Information on the maternal history of dysmenorrhea was obtained by questionnaires including visual analog scale (VAS) questions during the first antenatal care visit. The association of maternal history of dysmenorrhea and LBW was evaluated using logistic regression analyses adjusted for confounding factors (infant sex, maternal age, parity, pre-pregnancy body mass index (BMI) (kg/m²), gestational age, alcohol use during pregnancy, passive smoking, and occupational status).

RESULTS

Mothers with a history of dysmenorrhea were more likely to give birth to LBW infants (adjusted odds ratio (OR)=1.44; 95% confidence interval (CI): 1.12, 1.83). Among women with a history of dysmenorrhea, women ≥29 years old (adjusted OR 1.46; 95% CI 1.02, 2.10), multiparous (adjusted OR 1.59, 95% CI 1.12, 2.25), and women gave birth to female infant (adjusted OR = 1.53, 95% CI = 1.11, 2.11) had a higher risk of LBW.

CONCLUSIONS

As the first cohort study to investigate the association between maternal history of dysmenorrhea and LBW, our study shows that dysmenorrhea may increase the risk of LBW.

Role of uterine forces in intrauterine device embedment, perforation, and expulsion

BACKGROUND

The purpose of this study was to examine factors that could help reduce primary perforation during insertion of a framed intrauterine device (IUD) and to determine factors that contribute in generating enough uterine muscle force to cause embedment and secondary perforation of an IUD. The objective was also to evaluate the main underlying mechanism of IUD expulsion.

METHODS

We compared known IUD insertion forces for "framed" devices with known perforation forces in vitro (hysterectomy specimens) and known IUD removal forces and calculated a range of possible intrauterine forces using pressure and surface area. These were compared with known perforation forces.

RESULTS

IUD insertion forces range from 1.5 N to 6.5 N. Removal forces range from 1 N to 5.8 N and fracture forces from 8.7 N to 30 N depending upon device. Measured perforation forces are from 20 N to 54 N, and calculations show the uterus is capable of generating up to 50 N of myometrial force depending on internal pressure and surface area.

CONCLUSION

Primary perforation with conventional framed IUDs may occur if the insertion pressure exceeds the perforation resistance of the uterine fundus. This is more likely to occur if the front end of the inserter/IUD is narrow, the passage through the cervix is difficult, and the procedure is complex. IUD embedment and secondary perforation and IUD expulsion may be due to imbalance between the size of the IUD and that of the uterine cavity, causing production of asymmetrical uterine forces. The uterine muscle seems capable of generating enough force to cause an IUD to perforate the myometrium provided it is applied asymmetrically. A physical theory for IUD expulsion and secondary IUD perforation is given.

Dysmenorrhea

Primary dysmenorrhea is commonly a straightforward diagnosis that can be made accurately with an attentive history. In young women who have classic symptoms and no specific indication, a pelvic examination is often unnecessary in the initial evaluation. The opportunity for primary care practitioners to support women in unearthing the best approach to this chronic recurrent discomfort to minimize adverse life impact is significant and valuable. Identification of patients who are incapacitated by their symptoms or have symptoms that represent underlying pathology is a critical component of a careful history. The wide range of treatments available for primary dysmenorrhea virtually ensures that all females troubled by the symptoms can find relief with safe and inexpensive treatments while limiting negative side effects.

Myometrial oxytocin receptor mRNA concentrations at preterm and term delivery - the influence of external oxytocin

The hormonal system for induction of term and preterm labour is not fully understood. Therefore, we investigated myometrial gene expressions for neurohypophyseal hormones and their receptors, prostaglandin F(2alpha) and ovarian steroid receptors in women delivered by Caesarean section. Myometrial tissue for real time PCR was collected from 39 women delivered at term before and after the onset of labour and preterm. Women delivered electively at term had significantly higher oxytocin receptor mRNA expressions (2.52 +/- 0.37 oxytocin receptor/actin; median +/- SEM) than those delivered with ongoing labour at term (1.01 +/- 0.34; p = 0.015) and those at preterm (1.08 +/- 0.25; p = 0.004). Sub-analyses revealed that the difference at term pregnancies solely was related to patients receiving oxytocin during labour (p = 0.007). These patients had higher oxytocin peptide mRNA levels than those without labour at term (p = 0.009). PGF(2alpha) receptor mRNA concentrations were 27.80 +/- 3.55, 11.46 +/- 2.87 and 19.54 +/- 5.52 PGF receptor/actin, respectively, for the groups. Women without labour at term had higher concentration than those with labour (p = 0.005). Our results suggest that oxytocin, its receptor and the PGF(2alpha) receptor are involved in the regulation of labour through a paracrine mechanism.

Dysmenorrhea in adolescents: diagnosis and treatment

Dysmenorrhea occurs in the majority of adolescent girls and is the leading cause of recurrent short-term school absence in this group. In the vast majority of cases, a presumptive diagnosis of primary dysmenorrhea can be made based on a typical history of low anterior pelvic pain coinciding with the onset of menses and lasting 1-3 days with a negative physical examination. Risk factors for primary dysmenorrhea include nulliparity, heavy menstrual flow, and smoking. Poor mental health and social supports are other associations. Empiric therapy for primary dysmenorrhea can be initiated without diagnostic testing. Effective therapies include NSAIDs, oral contraceptives, and pharmacologic suppression of menstrual cycles. In atypical, severe, or refractory cases, imaging and/or laparoscopy should be performed to investigate secondary causes of dysmenorrhea. The most common cause of secondary dysmenorrhea is endometriosis, the treatment of which may include medical and surgical approaches. Pharmacologic treatment of young women with pain related to endometriosis is similar to treatment of primary dysmenorrhea but may infrequently include gonadotropin-releasing hormone agonists in severe refractory cases.

Targeting the oxytocin receptor to relax the myometrium

Oxytocin acting via its receptor is involved in the myometrial hyperactivity of preterm labour and possibly also in that of primary dysmenorrhoea. The closely related hormone vasopressin acting on its uterine receptor of type V1a may also contribute to the myometrial hyperactivity of these conditions. Several pharmaceutical compounds inhibiting these receptors are, therefore, under development and one substance, atosiban, has now been registered in many countries for the treatment of preterm labour. This compound blocks both the oxytocin and the vasopressin V1a receptor. The efficacy is at least as pronounced as that of other types of drugs and side effects are much reduced. In this overview, present knowledge about receptor-mediated effects of oxytocin and vasopressin on myometrial activity is summarised. Furthermore, the therapeutic use of oxytocin and vasopressin V1a receptor antagonists in preterm labour and primary dysmenorrhoea is discussed.