Creatine kinase, platelet aggregation, and bleeding risk in women with uterine leiomyomas

Excessive menstrual blood loss in the presence of uterine leiomyomas occurs
frequently, but there is a lack of clinical studies that assess the potential
causes of this excessive bleeding.
We hypothesize that relatively high plasma enzyme creatine kinase (CK) might
increase bleeding risk. The enzyme is the main ADP scavenger in plasma, as it
catalyses the reversible transfer of a phosphorylgroup from creatine phosphate
(CrP) to ADP, creating ATP in the reaction:

CrP + ADP <-> Creatine + ATP

As ADP is central to platelet aggregation, high CK activity might lead to
reduced ADP and thus inhibit platelet aggregation in a clopidogrel-like effect.
ADP activates platelets in synergy with other platelet agonists such as
collagen, epinephrine, and low concentrations of thrombin. The importance of
ADP is evident from the bleeding risk in patients with so-called platelet
storage pool disease, a condition with a reduced content of the platelet
granules including ADP. Removal of ADP by CK, especially in the presence of
CrP, is therefore likely to result in impaired platelet aggregation and thus an
increased bleeding risk.
Plasma CK activities are particularly high in women of African ancestry as
compared to European ancestry, additionally, a locally higher activity of CK is
found in leiomyomas. Therefore, it is desirable to study the hypothesized
greater bleeding risk associated with CK in these women with monthly heavy
menstrual bleeding.

Rationale of pilot study:
We recently reported that increased activity of the ADP-consuming enzyme
creatine kinase (CK) activity is associated with reduced platelet aggregation
in healthy male volunteers. By inhibiting platelet aggregation CK could promote
bleeding. The activity of CK and other ADP-consuming enzymes such as adenylate
kinase (AK) in menstrual blood and its effect on bleeding severity remains
unclear. A high activity of ADP-consuming enzymes could be a contributing
factor in heavy menstrual blood loss or postpartum haemorrhage. To our
knowlegde, the measurement of CK and other ADP-consuming enzymes in menstrual
or postpartum blood has not been studied previously. Prior to the main study,
we will perform a feasibility pilot of CK/AK measurement in menstrual and
postpartum vaginal blood, and compare the CK and AK activity in vaginal blood
to venous plasma CK/AK activity, platelet aggregation and bleeding severity
(also see the Appendix of the protocol).
Finally, as we are collecting menstrual blood, we would like to test whether we
can measure DOAC (direct oral anticoagulant) and VKA (vitamin K antagonist)
concentration in menstrual blood. In the further we might conduct a study on
the effect of DOAC*s and VKA*s on menstrual bleeding.

Main study:
We want to assess whether bleeding risk in women with uterine leiomyomas is
associated with CK activity and attenuated platelet aggregation.


Objective of pilot study:
Firstly, to perform a feasibility pilot of CK/AK measurement in menstrual and
postpartum vaginal blood. Secondly, to compare CK and AK activity in vaginal
blood to venous plasma CK/AK activity, platelet aggregation and bleeding
severity. Thirdly, the concentration of DOAC and VKA in menstrual blood.

Observational study

Participant will be ask to visit the Academic Medical Centre twice.
Venous blood will be drawn (50 mL) for platelet and coagulation test, and for
CK estimations. Participants will be asked to collect menstrual blood once.
Assessing the presence/absence of uterine leiomyomas will be done performing a
transvaginal ultrasound once. During the ultrasound unexpected findings may
occur, such as ovarian or uterine abnormalities; participants should be aware
of, next to the identification of leiomyomas, the diagnostic character of this
tests with its potential findings and consequences. When an unexpected finding
does occur the gynaecologist will discuss this with the participant and
initiate further care.
The risk and burden of these assessment are small. Assessing whether CK is
associated with increased bleeding risk in these women might eventually lead to
completely novel, conservative treatment options with CK inhibitors in women
with uterine leiomyomas.


With the pilot study, we aim to get more clarity in the assessment of CK and AK
activity in vaginal blood loss. When the measurements are thought to be
feasible and contributory, in a larger study the association between menstrual
and postpartum blood CK and AK activity, platelet aggregation and bleeding
severity can be further explored.