A new classification of ovulatory disorders for making ‘a precise diagnosis’

Published 16 February 2023

Following many years of classifying ovulatory disorders into groups largely based on hormone levels, FIGO has now presented a new classification system based on anatomical origin (hypothalamus, pituitary and ovarian), and with PCOS now defined in a separate fourth group.

Towards the end of 2022 the International Federation of Gynecology and Obstetrics (FIGO) published a new classification of ovulatory disorders whose systematic structure was based on three anatomical categories - hypothalamus, pituitary and ovary - with PCOS added as a fourth group.(1) The last was recognised as ‘a separate category’ because its diagnosis appeared independent of hormone levels. ‘Women with PCOS often have levels of FSH and LH in the normal range,’ explained the publication, noting that the overall classification of ovulatory disorders remains dominated by historical definitions dependent on hormone levels (gonadotrophins and estradiol). Since publication of these early classifications, which were based largely on that of the WHO from 1973, there have been advances in understanding of the pathology of ovulatory disorders, their diagnosis, and resolution. ‘There exists a need for a more comprehensive and updated classification,’ explained the FIGO working group.

And that need remains as great as ever, noted FIGO, which listed a catalogue of common ovulatory disorders likely to affect quality of life and disrupt menstrual cycles and fertility, notably evident in abnormal uterine bleeding, which FIGO had already addressed in two classification systems.(2) The former addressed frequency, regularity, duration and volume of menstrual blood loss, while the second addressed the potential causes, adopting an anatomical framework which is similarly proposed in the new classification system (with its addition of the new category of PCOS). To aid clarification, the new anatomical system was summarised with the acronym HyPO-P (hypothalamus, pituitary, ovary and PCOS).

The published paper devotes much space to how consensus was reached - by application of a five-round Delphi process under the management of a FIGO steering committee. Participants responding to the rounds of Delphi questions included national societies, specialist groups (reproductive endocrinologists and their journals), individual experts and public representatives (for the final round of questions). Consumer groups were questioned in the fifth and final round of questions - after the first draft of the classification was completed. The decision to classify PCOS in a separate category - while puzzling to some of the lay representatives - was largely accepted by the experts in the second round of questions. PCOS is ‘a complex and heterogeneous condition with comprehensive international guidelines for diagnosis, investigation, and management that cannot be confined to an ovarian origin,’ the report noted.

In addition, the final classification subdivided each of the three anatomically defined categories (ie, without PCOS) into ten further mechanisms by which cause might be explained: thus, hypothalamic to genetic, autoimmune, iatrogenic and neoplasm; pituitary to functional infectious/inflammatory, trauma/vascular; and ovarian to physiological, idiopathic and endocrine.

Despite its apparent complexity, the system, said FIGO, is designed to ‘harmonise definitions and categories . . . and improve the ability of basic, translational, clinical, and epidemiologic research to advance our knowledge of ovulatory disorders, their diagnosis, and their management’.

Although the classification ‘has general support’, there have already been somewhat critical comments, notably from two endocrinologists whose influence reaches way back to the first ESHRE/ASRM diagnostic consensus on PCOS (the ‘Rotterdam criteria’) and even to the original WHO classification system of the 1970s. In a journal commentary on the FIGO system Bruno Lunenfeld and Bart Fauser claim that the anatomical FIGO approach was misguided, and would have served patients better if its staring point was ‘relevant complaints of women’, and from there to plot a diagnostic and management path.(3) This, they propose, represents ‘current thinking’ - from diagnosis to prognosis - and would incorporate ‘big data, e-health tools concerning individual symptoms, biometrics, improved hormone assays (including AMH), patient-led monitoring of cycle variability and lifestyle factors’. This, they argue, would take a more practical (public health) approach and focus on the most common conditions.

However, in supporting the new system - and in something of a rebuttal of the claims of Lunenfeld and Fauser - two of the FIGO steering committee insist that the new system offers ‘a logical framework’ in which to serve patients and by which a precise diagnosis may be made for any woman presenting with features of an ovulatory disorder. Logical, maybe, but in its subdivision of the three anatomical groups into ten further sources of cause (genetic, autoimmune, iatrogenic, neoplastic, functional, inflammatory/infectious, trauma and vascular, physiological, idiopathic, and endocrine) the system takes on a complexity which, the authors advise, is best remembered by the aide-memoire GAIN FIT PIE!

1. Munro MG, Balen AH, Cho S, et al. The FIGO Ovulatory Disorders Classification System. Hum Reprod 2022; 37: 2446-2464.
2. Munro MG, Critchley HOD, Fraser IS; FIGO Menstrual Disorders Committee. The two FIGO systems for normal and abnormal uterine bleeding symptoms and classification of causes of abnormal uterine bleeding in the reproductive years: 2018 revisions. FIGO Committee on Menstrual Disorders. Int J Gynaecol Obstet 2018; 143: 393–408.
3. Balen AH, Munro MG, O’Neill HC, Lunenfeld B, Fauser BCJM. The New FIGO Ovulatory Disorder Classification: PRO and CON. Fertil Steril 2023; doi.org/10.1016/j.fertnstert.2023.01.043

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