• Number of days with bleeding/spotting; Number of bleeding/spotting episodes; Number of days with a certain bleeding intensity (e.g. bleeding intensity =2); [ Time Frame: 52 weeks ] [ Designated as safety issue: Yes ]
• Length of bleeding free intervals; Amenorrhoea yes/no (absence of spotting and bleeding); Absence of bleeding yes/no; [ Time Frame: 52 weeks ] [ Designated as safety issue: Yes ]
• QualiPause Inventory (domains: psychological, vasomotor, somatic, sexual, menstrual, androgenic): average score of the single items within the domain; QualiPause Inventory 7D: weighted sum score of the symptoms [ Time Frame: 52 weeks ] [ Designated as safety issue: No ]

The purpose of this study is to demonstrate endometrial safety of continuous combined 0.5 mg estradiol and 2.5 mg dydrogesterone.

Inclusion Criteria:

• Amenorrhoea for >= 12 months.
• Serum estradiol and FSH level within the postmenopausal range
• Baseline endometrial biopsy assessed by light microscopic histological evaluation revealing: insufficient endometrial tissue for diagnosis because of insufficient available (atrophic) endometrial tissue (not because of an inaccessible cervix) and endometrial thickness < 5 mm (double layer) by transvaginal ultrasound, atrophic endometrium, secretory endometrium, menstrual type endometrium, proliferative endometrium

Exclusion Criteria:

• Previous systemic unopposed estrogen replacement therapy over 6 months or more.
• Any estrogen, progestogen, and/or androgen therapy in the last four weeks before Screening Visit (Visit 1). The baseline endometrial biopsy should in all cases be taken after cessation of the withdrawal bleeding due to previous hormone replacement therapy.
• History or presence of an estrogen dependent neoplasia (including breast- cancer).
• History or presence of malignant neoplasms other than basal or spinal cell carcinoma of the skin.