Editorial
Current Data about the Development of Hypoparathyroidism after Thyroid Surgery
Pietro Caglià* and Silvana Puglisi
Department of Medical and Surgical Sciences, G Ingrassia University of Catania, Italy
*Corresponding author: Pietro Caglià, Department of Medical and Surgical Sciences, Advanced Technologies G. Ingrassia University of Catania, Via S. Sofia 86, 95123 Catania, Italy
Published: 03 Aug, 2017
Cite this article as: Caglià P, Puglisi S. Current
Data about the Development of
Hypoparathyroidism after Thyroid
Surgery. Clin Surg. 2017; 2: 1577.
Editorial
Hypoparathyroidism and the resulting hypocalcemia is a common iatrogenic complication
following surgical procedures to the neck, and commonly, to the thyroid gland [1,2]. In spite of
many improvements in surgical techniques to avoid hitting and damaging the parathyroid glands,
hypoparathyroidism remains a significant postoperative morbidity after total thyroidectomy. This
specific complication, as well as recurrent laryngeal nerve injury, is feared, because it may give rise
to significant and sometimes permanent, disability for the patient [3]. Postoperative hypocalcemia
negatively impacts a patient’s quality of life, not only with a prolonged hospitalization, the need for
life-long calcium supplementation, but also increasing the risk of medical disputes. Considerable
efforts have been spent preventing post-operative hypoparathyroidism after thyroidectomy, but
its consequences remain widely undervalued [4]. The amount of publications on post-surgical
hypoparathyroidism suggests that the problem has a high impact on health and social life either
for patients and surgeons. Costs to society in terms of medical treatment, follow-up, including
frequent and repeated laboratory testing and treatment and sick leave, are considerable [5]. Many
factors may be involved in the onset of hypocalcemia and hypoparathyroidism after thyroid
surgery, including total thyroidectomy, reoperation, neck dissection, preoperative hyperthyroidism,
autoimmune and inflammatory thyroid disease and surgical procedure performed by inexperienced
surgeons [6]. However not all patients with these factors will develop such complication, probably
because in order for it to happen, concur other causes, whose identification seems fundamental
to its prevention. The incidence of post-surgical hypoparathyroidism is difficult to define and
the literature review shows a considerable variation in the reported data. Hypocalcaemia after
thyroidectomy ranges in fact between 1 to above 50% [7,8]. Separately considering, transient and
permanent, hypoparathyroidism are reported to be 6.9 to 38 % for the former, and 4 to 10.6% for the
latter but at the worst, these rates were as high as >60 and 33 %, respectively [9]. The definition of
hypoparathyroidism varies widely in literature in terms of calcium level, need for supplementation
of calcium and/or vitamin D [10,11]. Furthermore, different time points have been used to
determine when postoperative hypoparathyroidism should be classified as transient or permanent.
Some consider postoperative parathyroid glands injury to be permanent if recovery of function has
not occurred within 6 month, whereas others define permanence at 1 year after surgery. However it
should be remembered that using an earlier time point could result in classifying some patients as
permanently hypocalcemic when they could still show resolution of their condition [7,12]. All this
is reflected on a wide incidence of hypoparathyroidism reported in different series where transient
and permanent hypocalcaemia ranges from 1.6–60% to 0.9–33% respectively. The problem of early
and accurate prediction of postoperative hypocalcaemia has also been discussed in great detail.
Early prediction also helps in identifying “at risk patients” requiring early calcium and vitamin
D supplementation. Many efforts have been done to early assess the postoperative parathyroid
function, and there are several reports that postoperative PTH level is a useful tool for predicting
hypocalcemia [13,14]. Particular attention has been paid to lowering PTH level immediately
or several hours postoperatively. The rapid PTH assay can virtually reflect real time parathyroid
function because the short half-life of PTH [15]. However, intraoperative PTH assay is not available
in all centers for its cost. Furthermore, operation time can be prolonged, because it needs time.
Usually post-operative serum calcium levels are used to predict hypoparathyroidism and other
authors reported that a gradual increase of calcium level within 24 hours postoperatively predicts
normal calcium levels [16]. Regarding the correlation between postoperative hypocalcemia and the
number or the viability of in situ preserved parathyroid glands many reports are available in literature
[17]. Although physical preservation of the parathyroid glands in situ is necessary, it does not ensure
normal parathyroid function owing to vascular injury of the glands. A wide consensus exists about
the transplant of the parathyroid gland that seems to be nonviable [18]. Moreover some surgeons, in order to prevent permanent hypoparathyroidism, advocated routine
parathyroid autotransplantation [18,19]. Although a color change
from the normal brownish-red to blue-black has traditionally been
thought to be a sign of vascular involvement and impaired function,
recent studies have questioned this method [7,20]. Others Authors
have shown that bleeding from an incision of a parathyroid gland,
so-called ‘‘knife’’ test, is an important finding suggesting intact
vascularity [21].
Wishing to proceed to a discussion about the most common risk
factors we can certainly affirmed that the risk of hypoparathyroidism
increases with extent of thyroidectomy, malignant disease,
concomitant central and/or lateral neck dissection, autoimmune
or Graves’ disease and re-operation. Particularly it is reported that
the transient hypocalcemia after thyroidectomy for cancer ranges
from 13.6% to 75% and permanent hypoparathyroidism ranges
from 3.3% to 5.8% by placing the cancer as the main predictive
factor for the development of these complications. Moreover
the eventually associated lymphadenectomy increases the risk of
hypoparathyroidism. This conclusion is supported by the findings of
many Authors [22]. A significantly higher incidence of permanent
hypoparathyroidism was observed in patients with hyperthyroidism
but it is unclear exactly why in these patients thyroidectomies
have an increased rate of hypocalcaemia. Thyrotoxicosis was also
found to be a significant factor in several other studies exploring
hypocalcaemia and many authors indicate that Grave’s disease
and Hashimoto’s disease are to be considered a risk factor for
postoperative hypoparathyroidism. Reoperation may increase the
risk of iatrogenic injury to the parathyroid glands. The incidence of
transient and permanent hypocalcemia is reported up to 44.1 and
11% respectively. Given the high incidence of hypoparathyroidism
resulting from re-operation, surgeons should not be encouraged to
adopt hemi-thyroidectomy for unilateral benign disease. According
to the results of our study, the safety of the energy-based devices
is proved and their use in patients with thyroid diseases could be
appropriate [23]. Attention should be paid to using it at an appropriate
distance from vital anatomic structures such as recurrent laryngeal
nerves and parathyroid glands. Close to this important structures,
while performing thyroidectomy is highly recommended to use
conventional suture ligation technique in order to prevent damage to
the parathyroid glands [24].
Preservation of the parathyroid glands during total thyroidectomy
is the best prophylaxis to avoid postoperative hypocalcemia after total
thyroidectomy for an endocrine surgeon. Not always is necessary to
visually identify all parathyroid glands to accomplish this. Parathyroid
glands lying a slight distance from the thyroid are more difficult
to identify but easier to maintain functionally intact. Dissection at
the sub-capsular plane of the thyroid during total thyroidectomy
ensures preservation of most of the parathyroid, thereby lowering
the incidence of postoperative hypocalcaemia. Understanding the
complex vascular structures surrounding the parathyroid gland
is crucial to prevent post-thyroidectomy hypoparathyroidism
because there is no guarantee of normal postoperative parathyroid
function, even if the procedure is performed for benign disease.
In our opinion it is important for surgeons to think about second
surgery that may be performed in future for various reasons when
they perform hemi-thyroidectomy as an initial surgery. A careful
examination of the surgical specimen intraoperatively decreased the
incidence of inadvertent parathyroidectomy during thyroid surgery.
Any parathyroid gland that looks likely to be totally devascularized
can be removed during the operation and autotransplanted into
well-vascularized muscles such as the sternocleidomastoid muscle.
Evaluation and management of central neck surgical patients for
postoperative hypoparathyroidism may present challenges. Although
the dissection of central compartment is a safe procedure, it is
difficult to keep the parathyroid glands intact in case of a tumor is
large, infiltrative or if there is extensive lymph node metastasis. In
this case, a careful staging should be performed in order to avoid
possible morbidity related to reoperation for recurrence involving
lymph node. Resolution of hypoparathyroidism is likely to be related
to recovery of the parathyroid glands function. Nowadays is it
difficult to predict which patients will recover and it is also unclear
as to whether any specific intervention will facilitate recovery.
Furthermore, 12 months may be the most appropriate time point
to define hypoparathyroidism as a permanent condition because
patients with transient postoperative failure of parathyroid glands
usually resolved within a year after surgery. A low PTH level early
after total thyroidectomy is associated with a high risk of permanent
hypoparathyroidism and normal levels usually exclude long-term
parathyroid glands dysfunction. However, the cost of the PTH assay
may limit its widespread application. Finally, hypoparathyroidism
following thyroidectomy is a documented source of complaints and
medical disputes. Appropriate informed consent remains a priority
to emphasize particularly the importance of some primary factors
responsible for the increased risk of unintended injury of parathyroid
glands after thyroid surgery.
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