Perimenopause and PCOS: When Symptoms Overlap and How to Tell Them Apart
PCOS and perimenopause can occur together or be confused for each other. This guide explains how their symptoms overlap and what distinguishes them.
A Challenging Diagnostic Overlap
Polycystic ovary syndrome (PCOS) and perimenopause affect women at different life stages, but because many women with PCOS enter perimenopause in their 40s, the two conditions frequently intersect. This creates a genuine diagnostic challenge. Symptoms of perimenopausal hormonal transition can mask or mirror those of PCOS, and vice versa. Women with existing PCOS may find their symptoms change, worsen, or shift in character as perimenopause begins. Others may receive a new PCOS diagnosis for the first time in their 40s, only to discover perimenopause is also contributing. Untangling the two requires specific investigation rather than assumption.
Core Features of PCOS
PCOS is defined by the Rotterdam criteria, which require at least two of three features: irregular or absent ovulation, clinical or biochemical signs of excess androgens (such as acne, hirsutism, or raised testosterone), and polycystic ovarian morphology on ultrasound. PCOS is a lifelong hormonal condition, not a phase of transition. It is associated with insulin resistance, elevated androgens, and a specific hormonal pattern. Many women with PCOS have higher baseline LH relative to FSH, lower oestrogen, and higher androgens than women without the condition. PCOS does not go away in perimenopause, though its presentation may change significantly.
How Perimenopause Changes PCOS Symptoms
When a woman with PCOS enters perimenopause, the already-irregular cycle becomes harder to interpret. Cycles that were previously long or irregular may become even more unpredictable. Hot flashes and sleep disturbance, typical perimenopausal symptoms, can appear on top of pre-existing PCOS symptoms. Some research suggests that women with PCOS may experience a later onset of menopause because their ovaries have a larger antral follicle count, effectively a larger reservoir of follicles. This means some women with PCOS have longer perimenopausal transitions. Interestingly, some PCOS-related symptoms such as hyperandrogenism may reduce as perimenopause progresses and oestrogen levels fall.
Distinguishing Features
Hot flashes and night sweats are characteristic of oestrogen decline in perimenopause and are not features of PCOS itself. Vaginal dryness and genitourinary changes are perimenopause-specific. Elevated androgens, insulin resistance, and dark patches of skin (acanthosis nigricans) point toward PCOS. An ovarian ultrasound showing polycystic morphology in a woman under 40 supports PCOS, though this finding becomes less reliable for diagnosis in women over 35 as antral follicle counts naturally decline with age. FSH levels are key: perimenopausal transition is associated with rising FSH, while PCOS is typically associated with normal or elevated LH and normal or low FSH.
Investigations That Help Distinguish the Two
Blood tests are central to separating these conditions. FSH, LH, oestradiol, testosterone (total and free), SHBG, DHEAS, fasting insulin, and fasting glucose all provide relevant information. A pelvic ultrasound assesses ovarian morphology. AMH (anti-Mullerian hormone) is elevated in PCOS and may also help assess ovarian reserve during the perimenopausal transition. The clinical picture, including age, symptom history, menstrual pattern, and the presence or absence of signs of androgen excess, helps frame the interpretation of results. Because both conditions can coexist, investigations should be designed to characterise both rather than assuming one rules out the other.
Managing Both Conditions Together
When PCOS and perimenopause coexist, management must address both. HRT can help perimenopausal symptoms and may have a beneficial effect on insulin sensitivity, though careful progestogen selection matters in women with PCOS, as some synthetic progestogens worsen insulin resistance. Body-identical progesterone is often preferred. Lifestyle measures including resistance exercise, a lower glycaemic diet, and maintaining a healthy weight remain important cornerstones for managing both conditions. Women managing this combination benefit from a gynaecologist or menopause specialist with specific knowledge of PCOS to ensure treatment is tailored rather than generic.
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