As far as the
occurrence or non-occurrence of ovulation in the course of the ovarian
cycles is concerned, women present both ovulatory ( biphasic ) and anovulatory
( monophasic ) cycles.
In the ovulatory cycles the
complete follicular development takes place, resulting in the growth of
a mature follicle, ovulation and formation of the corpus luteum. These
cycles are considered biphasic because they present a follicular ( estrogenic
) and a luteal ( progesteronic-estrogenic ) phase. Along the follicular
phase, the ovary produces mostly estrogens, while along the luteal one
it produces progesterone and estrogens.
Conversely, in the anovulatory cycles obviously there is no ovulation
and, as a consequence, the formation of the corpus luteum does not take
place. In this way, these cycles are monophasic, since they exhibit only
the follicular phase, which is characterized by variable degrees of persistent
As to the cases of "LUF"
( luteinized unruptured follicles ), we must remark that, despite also
constituting a kind of failure in the ovulatory process, they must not
be included in the usual category of anovulatory cycles because their
histological and endocrine features differ too much from these ones, since
these features are similar to those of the ovulatory cycles ( see
Note 1, below ).
In this way, whenever
I speak of anovulatory cycles I mean the specific kinds of ovarian and
menstrual cycles that exhibit only the follicular phase, since
in these cycles both ovulation and formation of the corpus luteum do
not take place. Endocrinally and histologically they are monophasic
cycles. Only follicles in variable stages of growth and involution can
be found in the ovaries throughout these cycles.
Anovulatory cycles ( monophasic
) are physiologically normal soon after menarche, and are part of the
process of maturation of the hypothalamus-pituitary-ovaries axis. This
maturation is considered complete with the establishment of regular ovulatory
cycles. Even so, we must remark that the occurrence of anovulatory cycles
intermingled with the ovulatory ones is frequent and normal along the
fertile years of a woman's life. In this way, we can say that there are
women who ovulate more often, while others ovulate less often.
In the absence of hyperestrogenism,
hyperprolactinemia, hyperandrogenic syndromes and the usually named "polycystic"
pathologies of the ovaries, the occurrence of occasional anovulatory cycles
with a regular duration intermingled with the ovulatory ones is considered
normal ( see Note
2, below ).
We must also remark that, in the years that precede menopause, ovulation
gradually becomes less frequent and even rare, and the anovulatory cycles
predominate again. While
in puberty the frequent occurrence of anovulatory cycles is due to the
process of maturation of the hypothalamus-pituitary-ovaries axis, in pre-menopause
the predominance of anovulatory cycles is a result of the progressive
depletion and exhaustion of the ovaries.
There are the more varied possible patterns of follicular growth in the
anovulatory cycles, with or without the formation of the mature follicle
( or follicle at the third stage of growth ). The duration of these cycles
also may exhibit great variations, from the normal average of 25-32 days
up to short cycles ( less than 25 days ) and long ones ( 35 to 50 days,
or even more ). Therefore, there are several kinds of anovulatory cycles.
Though anovulatory cycles often tend to be irregular and exhibit variable
patterns of follicular growth, there are also the common anovulatory
cycles, characterized by the formation of a mature follicle ( or almost
mature ) and duration within the limits of normality. Anovulatory cycles
of this kind are relatively frequent throughout the menacme ( the period
of women's lives in which they menstruate ) and, due to their characteristics,
they are not perceived as such by women, who usually have no awareness
of their occurrence. In practice, they only can be detected through a
careful gynecologic study.
In these common anovulatory
cycles the mature follicle may reach its usual size, but there is
a failure in the ovulatory mechanism that results in the absence of the
pituitary ovulatory peak of LH ( luteinizing hormone ). Because of this,
there is no follicular rupture and the growing follicle persists as such
for more 10 to 14 days, after which its process of follicular involution
and atresia ( death ) begins. This results in the sudden fall of the estrogen
levels and the consequent coming of menstruation.
Botella Llusiá remarks that in the common anovulatory cycles,
"... the atresia and decay of the follicle takes place in such a
way that the menstrual rhythm does not alter" ( "Tratado
de Ginecologia, Tomo 3 - Enfermedades del Aparato Genital Femenino"
- Editorial Científico-Médica, Barcelona, 1965 ).
Nevertheless, there are also reports of regular anovulatory cycles in
which signs of mature follicles cannot be detected.
On the other hand, long-lasting
anovulatory cycles are often related to the prolonged persistence of mature
follicles or to the usually named "polycystic" pathologies of
the ovaries. Several endocrine disorders in the hypothalamus-pituitary-ovaries
axis are responsible for chronic anovulation, long-lasting cycles ( oligomenorrhea
) and even amenorrhea.
It is also important to remark that, though many anovulatory cycles progress
normally and without problems ( mostly those named common anovulatory
cycles ), a considerable number of these cycles characterized by absence
of ovulation tend to be associated with several degrees of relative or
absolute hyperestrogenism, a condition that may cause endometrial hyperplasias.
These endometrial hyperplasias, in turn, are very frequent causes of prolonged
and/or excessive menstrual bleedings ( hypermenorrhea and/or menorrhagia
Chronic anovulation - which is different from the normal occurrence of
some anovulatory cycles intermingled with the ovulatory ones - is obviously
associated with infertility and, many times, with hyperestrogenism and
endometrial hyperplasias. Endometrial hyperplasias require special medical
attention in order to prevent a possible further development of endometrial
cancer - though, fortunately, most of them are entirely benign and very
frequent in the daily gynecologic practice. As I said above, the main
clinical manifestations of endometrial hyperplasias are prolonged and/or
excessive menstrual bleedings.
1: There are cases of luteinization of follicles that do not
ovulate, condition known as "LUF" ( luteinized unruptured follicles
). This is a very special sort of failure in the ovulatory process in
which, despite the absence of follicular rupture and ovulation, the unruptured
follicle becomes luteinized under the action of the LH ( luteinizing hormone
), giving rise to the corpus luteum. In such cases both the production
of progesterone and the duration of the luteal phase of the cycle may
be normal. Cases of "LUF" constitute, therefore, a very special
kind of ovulatory failure with biphasic cycles.
2: a) hyperestrogenism:
excessive production of estrogens or excessive estrogenic activity; b)
hyperprolactinemia: a disorder characterized by an excessive production
of prolactin; c) hyperandrogenic syndromes: disorders characterized
by an excessive production of androgens; d) as to the so-called "polycystic"
pathologies of the ovaries ( "polycystic ovaries syndrome"
), I have some personal reservations regarding the use of the term "polycystic"
for such disorders. I think they would be much better defined as "polymicrocystic
ovaries." As to that condition, see my article "Polycystic
is a gynecologist dedicated to Clinical, Preventive and Psychosomatic
Gynecology. Graduated in 1974 by Faculdade de Medicina da Universidade
Federal do Rio de Janeiro, he is the author of several articles published
in medical journals and of the books "Novas
Perspectivas em Ginecologia" ("New Perspectives in Gynecology")
and "Os Órgãos Sexuais Femininos:
Forma, Função, Símbolo e Arquétipo" ("The
Female Sexual Organs: Shape, Function, Symbol and Archetype"),
published by Imago Editora, Rio de Janeiro, 1990, 1993.
] [ Consultório
(Medical Office) ] [ Obras
Publicadas (Published Works) ]
Perspectivas em Ginecologia (New Perspectives in Gynecology)
Órgãos Sexuais Femininos (The Female Sexual Organs)
Polêmicos (Polemical Subjects) ] [ Tópicos
Diversos (Other Topics)(Part 1) ]
Diversos (Other Topics)( Part 2) ] [ Tópicos
Diversos (Other Topics)(Part 3) ]
Diversos (Other Topics)(Part 4) ] [