Traditional adenomyosis (AM) pathology is indicated by the presence of ectopic endometrial glands and/or mesenchymal stroma, with growth at least 2.5 mm below the endometrial-myometrial interface (EMI) [1] within the endometrium. The development of such structures is due to a combination of factors along with adjacent smooth muscle proliferation, resulting in limited or diffuse hypertrophy of the subfloor myometrium. AM is a common benign gynaecological disease of the uterus with increased menstrual flow, prolonged menstruation, progressive dysmenorrhoea and secondary infertility as the principal clinical symptoms [2, 3]. Such complications result from in limited or diffuse hypertrophy of the myometrium and loss of normal myometrial structure [4, 5]. Although benign in nature, adenomyoma can cause complications such as increased menstrual flow, dysmenorrhoea, and infertility due to the invasion of endometrial glands, as well as the mesenchyme, into the myometrium to form diffuse or confined lesions. Anatomically, adenomyoma is characterised by ectopic growth of normal endometrial tissue in the myometrium and compensatory hypertrophy of the smooth muscle of the myometrium, resulting in an enlarged uterus. In addition, anaemia and even dysfunction of vital organs such as the heart, brain, and lungs have been attributed to adenomyoma due to the increased blood loss of the patient during menstruation. Additionally, lower abdominal cramps, frequent urination, constipation, or difficulty in urination due to pressure from an enlarged uterus [6, 7, 8] can occur. These complications can exert a serious impact on the physical and psychological health of women.

Human epididymis secretory protein 4 (HE4) is an emerging tumor marker that is highly expressed in ovarian epithelial cell carcinoma but not in normal ovarian tissue. Immunohistochemical results showed that HE4 was expressed in 100% of endometrial cancers, 93% of plasmacytic adenocarcinomas, and 5% of clear cell ovarian cancers [9]. As with another cancer marker, carbohydrate antigen 125 (CA125), serum HE4 levels are elevated in more than 80% of ovarian cancer patients. In addition to being used as a tumor marker to screen for malignancy, HE4 has implications for the prognosis of ovarian cancer patients and for monitoring the outcome of postoperative treatment. Available studies [10] have largely focused on the significance of HE4 in the diagnosis and differentiation of benign and malignant ovarian cancer, and some have mentioned uterine AM in the literature only as a control group for ovarian cancer studies. Moreover, a few studies have noted the importance of HE4 in the diagnosis of uterine AM and its differential diagnosis with uterine fibroids. However, the expression of HE4 in ovarian endometriosis stemming from ectopic endometrium has been studied more in recent years. For example, some investigators have demonstrated that the level of HE4 in serum from patients with uterine fibroids is not statistically significant when compared with normal controls. Thus, HE4 is potentially useful as a differentiating indicator between uterine AM and uterine fibroids [11, 12]. Other studies have shown that HE4 is highly expressed in all stages of endometrial cancer, with no significant differences between stages [13]. This appears true in early stage endometrial cancer as HE4 is a more sensitive serum marker than CA125. Therefore, we speculate that HE4 and CA125 can be used as indicators to assess the outcome of patients with AM and/or adenomyoma.

At present, the principal treatment options for adenomyoma are surgery and pharmacological therapies. Surgical treatment options include hysterectomy or focal resection, both of which have proven clinically effective. However, surgical treatments can be traumatic for patients as hysterectomy is not only represents a loss of fertility for the patient, but also affects the blood supply to the ovaries [14]. These outcomes make it difficult for some patients to accept. Pharmacological treatment includes the use of prostaglandin inhibitors, danazol, progesterone, gonadotropin-releasing hormone agonist (GnRH-a), and blood stopping. In clinical practice, conservative treatment of uterine adenomyoma is largely based on GnRH-a, which depletes the presynaptic receptors of hypothalamic-pituitary transmission and produces a negative feedback effect. Specifically, GnRH-a inhibits gonadotropin release from the pituitary gland causing a decrease in luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels. This lowers the release of ovarian hormones resulting in low estrogen levels and a “reversible drug depot” phenomenon [15]. GnRH-a also reduces the blood supply to the patient’s uterine adenomyoma, thus achieving the desired therapeutic outcome of relieving symptoms such as dysmenorrhoea and reducing lesion size [16]. However, due to side effects and the tendency to relapse after discontinuation, patients’ compliance is generally poor. Moreover, long-term use of GnRH-a may result in bone loss due to low estrogen status and/or calcium in the body, and patients are prone to menopause-like symptoms such as night sweats and mood swings [17].

Dienogest (DNG) is a synthetic progestin, and a component of the contraceptive progestin, has only recently been introduced for the treatment of sub-terminal AM. Dienogest reduces the patient’s estrogen levels by mediating the hypothalamic-pituitary-ovarian axis, creating an inhibition of the ovarian endocrine system and simultaneously blocking the synthesis process of estrogen metabolizing enzymes [18]. Dienogest also has an anti-inflammatory effect and inhibits scarring and blood vessel formation, thereby directly inhibiting the creation of ectopic lesions [19]. Dienogest has both the pharmacological characteristics of a natural progestin and a synthetic hormone and greatly increases the activity of the progestin. After 3 months of administration, dienogest effectively improves the associated pain symptoms and is better tolerated by the patient [20]. A large number of studies and clinical data show that dienogest tken at 2 mg/day is safe and effective in the treatment of endometriosis, but its effectiveness in the treatment of sub-terminal AM is still in initial trials [21, 22, 23]. Based on this, the present study investigated the effect of combined treatment of GnRH-a and dienogest on the serum levels of HE4 and CA125 in patients with AM and adenomyoma, as well as the treatment efficacy of this therapeutic combination.

Adenomyoma is the most common benign tumor occurring in female reproductive organs. It is a common tumor in women from 30–50 years of age with the age of onset becoming younger in recent years. The principal manifestations of adenomyoma are increased menstrual flow and secondary dysmenorrhoea, which not only affects the patient’s physical health, but also her psychological well-being. The pathogenesis of adenomyoma is not fully understood, but studies have found that factors such as multiple abortions, intrauterine device (IUD) insertion, and caesarean sections are causative factors for adenomyoma [26, 27]. In addition, some studies have shown that elevated estrogen levels are also a cause of adenomyoma [28, 29, 30]. Although adenomyoma is benign in nature, it can cause complications such as increased menstrual flow, dysmenorrhoea, and infertility each of which can seriously affect women’s physical and psychological health. Moreover, adenomyoma can endanger their lives due to aggressive growth and consequential alteration of myometrial structure and malignancy-like biological behavior.

Gonadotropin-releasing hormone (GnRH) is a decapeptide neurohormone produced by the hypothalamus and is a key neuroendocrine regulator of the hypothalamic-pituitary-gonadal axis which plays an important role in the regulation of the reproductive system. GnRH-a is a derivative obtained by substituting amino acids at positions 6 and 10 in the natural structure of GnRH [31, 32, 33]. GnRH-a competes with GnRH for GnRH receptors in the anterior pituitary gland which depletes the number of GnRH receptors. This subsequently reduces the stimulatory effect of GnRH on the pituitary gland and inhibits gonadotropin release [34]. In clinical studies, GnRH-a is widely used in the treatment of uterine fibroids, endometriosis, AM, precocious puberty, assisted reproduction techniques, and preservation of fertility in chemotherapy patients. GnRH-a drug therapy is somewhat reversible and the clinical symptoms of AM tend to recur after discontinuation of the drug. Moreover, as the dosage of this type of drug is high, it is expensive, and the side effects are more pronounced for patients with uterine AM, patients have relatively poor drug adherence rates [35, 36, 37].

At present, much effort has focused on the creation of synthetic progestins with the dual properties of 19-nortestosterone and progesterone derivatives such as dienogest. Similar results have been obtained in trials of subendometriosis, where the efficacy of dinopregnanol, taken at 2 mg daily for 24 weeks, was comparable to that of sertraline in relieving the associated symptoms of pelvic pain, discomfort during intercourse, and low back pain. However, dinopregnanol reduced several symptoms including diastolic duct syndrome, reduced density, genital atrophy, and painful intercourse as well as symptoms that require the addition of small amounts of estrogen, including atrophy and painful intercourse, and increased tolerance and prolonged tolerance [38].

When comparing the efficacy of the two groups, the effective rate of the study group was 91.67% and the effective rate of the control group was 73.33%. When comparing between groups, the efficacy of the study group was higher than that of the control group (p 0.05). In the comparison of dysmenorrhea scores, the dysmenorrhea scores at 1, 3, and 6 months after treatment were lower in the study group than in the control group (p 0.05). The analysis suggests that GnRH-a alone only affects hormone levels and maintains low estrogen levels in patients by altering hormone secretion in the hypothalamic-pituitary-ovarian gonadal axis. GnRH-a also reduced the blood supply to the uterine adenomyoma lesions and thus shrank these lesions more slowly.

For larger adenomyomas, GnRH-a alone is not the best option [39, 40, 41, 42]. GnRH-a combined with dienogest can reduce the blood supply to the patient’s adenomyoma lesions by reducing the estrogen and blood supply to the adenomyoma lesions. The incidence of adverse reactions in the two groups was examined and there was no difference observed between the study group and the control group, and the data difference was not statistically significant (p $>$ 0.05). The safety of GnRH-a treatment alone, and in combination with dienogest, is also ensured as it is rapidly absorbed and metabolised by the kidneys and eliminated in the urine on a daily basis. Thus, there is no concern for the development of metabolic diseases associated with the accumulation of toxic side effects from long-term administration of this drug combination. Similarly, although the use of GnRH-a is associated with the hypoestrogenic side effects of the drug, which include hypoestrogenic syndrome, reduced density, genital atrophy, and painful intercourse. These side effects require the addition of small amounts of estrogen to reverse therapy, and these symptoms resolve normally with reverse therapy and do not affect the efficacy of the drug. National and international studies have found that GnRH-a alone, and in combination with dienogest, has achieved a high degree of safety and efficacy [43, 44].

CA125 is both a macromolecular glycoprotein and a membrane antigen. CA125 has been found to be present on the cell surface of ectopic endometrial lesions, and ectopic endometrium has a strong capacity to synthesize and secrete CA125 up to four times higher than in normal endometrium [45, 46, 47]. HE4 is secreted by ovarian cancer cells and has a molecular weight of approximately 12 kD compared to CA125 which has a molecular weight of 200,000 to 1 million kD. It has been hypothesized that this is the reason why HE4 is secreted into the bloodstream earlier and more readily than CA125 in ovarian cancer patients. Therefore HE4 is viewed as detecting ovarian cancer at an earlier stage. Combined with the results of this study, serum CA125 and HE4 levels in the study group were lower than those in the control group (p 0.05). Therefore, we believe that treatment with GnRH-a when combined with dienogest is more effective than single GnRH-a treatment. This study provides a new non-surgical treatment option for patients with adenomyoma and we will continue to increase the sample size and extend the follow-up period to observe the long-term outcome in terms of recurrence and fertility [48, 49].

In conclusion, the use of GnRH-a in combination with dienogest has shown a significant reduction in serum CA125 and HE4 levels, menstrual flow, dysmenorrhoea and change in lesion size in patients with AM and adenomyoma compared to the group receiving GnRH-a alone. The combination treatment regimen resulted in a more effective reduction in clinical symptoms, reduction in lesion size, and improved treatment efficiency. We conclude that GnRH-a, when combined with dienogest, is a superior choice for women with larger adenomyoma lesions requiring conservative treatment.

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

DGW and LMJ designed the research study. CLJ and MJS performed the research. LMJ and CLJ analyzed the data. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript. All authors have participated sufficiently in the work and agreed to be accountable for all aspects of the work.

This study was approved by Jinhua Hospital Zhejiang University School of Medicine Institutional Review Board (No. 2018-336), and all patients signed informed consent.

We would like to express our gratitude to all those who helped us during the writing of this manuscript.

This research was funded by Jinhua Science and Technology Bureau Project (No: 2021-3-126).

The authors declare no conflict of interest.