Perspective: Transient postparturient hypocalcemia-A lactation-induced phenomenon of high-producing dairy cows

Milk fever is one of the most historically relevant diseases of dairy cows. It is caused by tremendous calcium (Ca) expenditure at the initiation of lactation, so severe that cows can no longer stand and, if left untreated, die. Fortunately, through prepartum nutritional improvements, this version of clinical hypocalcemia is rare in the United States. Nonetheless, the opinion that all versions of postpartum hypocalcemia are detrimental remains pervasive, which is particularly significant given that 50% of cows are subclinically hypocalcemic after calving. This has led to a variety of available management and treatment strategies, ranging from prepartum dietary programs to postpartum Ca gels and boluses, targeted at preventing hypocalcemia in dairy cows. Recent research has determined that postpartum dairy cows can experience different types of subclinical hypocalcemia: transient, persistent, or delayed. We now know cows experiencing transient hypocalcemia as part of the homeorhetic adaptation to lactation are the highest milk producers in modern dairy herds, whereas cows with hypocalcemia several days after calving experience disease and losses in milk production. Therefore, it is wrong to assume all postpartum hypocalcemia is detrimental and that treatment of all cases is considered necessary and beneficial. Research indicates that milk synthesis at the onset of lactation contributes to immediate postpartum hypocalcemia, and that the mammary gland is a critical factor in management of Ca homeostasis. However, cows differ in their ability to manage this phenomenon, and it is possible that immediate postpartum influences such as dry matter intake, inflammation, and immune activation affect appropriate Ca regulation in the days following calving.

A Meta-Analysis of Risk Factors for Transient and Permanent Hypocalcemia After Total Thyroidectomy

Background

As hypocalcemia is the most common complication of total thyroidectomy, identifying its risk factors should guide prevention and management. The purpose of this study was to determine the risk factors for postthyroidectomy hypocalcemia.

Methods

We searched PubMed, Web of Science and EMBASE through January 31, 2019, and assessed study quality using the Newcastle–Ottawa Scale.

Results

Fifty studies with 22,940 patients met the inclusion criteria, of which 24.92% (5716/22,940) had transient hypocalcemia and 1.96% (232/11,808) had permanent hypocalcemia. Significant (P < 0.05) predictors of transient hypocalcemia were: younger age, female, parathyroid autotransplantation (PA), inadvertent parathyroid excision (IPE), Graves’ disease (GD), thyroid cancer, central lymph node dissection, preoperative severe Vitamin D deficiency, preoperative Vitamin D deficiency and a lower postoperative 24 h parathyroid hormone (PTH) level. Preoperative magnesium, preoperative PTH and Hashimoto’s thyroiditis were not significant predictors of transient hypocalcemia. IPE, GD, and thyroid cancer were associated with an increased rate of permanent hypocalcemia, but gender and PA did not predict permanent hypocalcemia.

Conclusion

Important risk factors for transient and permanent hypocalcemia were identified. However, given the limited sample size and heterogeneity of this meta-analysis, further studies are required to confirm our preliminary findings.

Truncal vs Branch Ligation of Inferior Thyroid Arteries in Total Thyroidectomy: Does It Affect Postoperative Hypoparathyroidism?

OBJECTIVE

Postthyroidectomy hypoparathyroidism remains a significant challenge. Truncal ligation of the inferior thyroid arteries (ITAs) may lead to an increased risk of hypoparathyroidism; however, dissection along the thyroid capsule with branch ligation of the thyroid arteries could be a safer option. This study's objective was to compare the effect of truncal versus branch ligation of the ITAs on the rate of postoperative hypoparathyroidism.

STUDY DESIGN

Randomized prospective trial in line with the CONSORT guidelines.

SETTING

The study was conducted at a high-volume tertiary care setting.

METHODS

We randomized 319 patients into 2 groups: truncal ITA ligation (n = 157) and branch ITA ligation (n = 162). The primary outcomes were serum calcium and parathormone levels on the second postoperative day, followed by the levels on months 1, 3, 6, and 12. The need for exogenous replacements was noted. The secondary outcomes, such as operative time, blood loss, and other complications, were also recorded.

RESULTS

Our study revealed a significant difference in the incidence of transient hypocalcemia in patients undergoing truncal ITA ligation and branch ITA ligation (22.9% vs 3.1%, P < .05). The results showed that the levels of serum calcium and parathormone dropped on the second postoperative day and that 36 patients from the truncal ITA ligation group required exogenous calcium and vitamin D replacement. In contrast, only 5 patients from the branch ITA ligation group required the same.

CONCLUSIONS

This is the largest randomized trial of patients undergoing thyroidectomy, and it shows that dissection along the thyroid capsule with branch ligation of the ITAs is more likely to preserve parathyroid function as opposed to truncal ligation of ITAs.

Analysis of the factors that have an effect on hypocalcemia following thyroidectomy

OBJECTIVE

The incidence of and risk factors for hypocalcemia following thyroidectomy were evaluated in this study.

MATERIAL AND METHODS

One hundred and ninety thyroidectomy patients were evaluated retrospectively for factors that might contribute to postoperative hypocalcemia; age, hyperthyroidism, malignancy, the extent of surgery (total/near total/subtotal thyroidectomy), cervical lymph node dissection, and incidental parathyroidectomy.

RESULTS

The rate of transient hypocalcemia/hypoparathyroidism was 19.47%, with a permanent hypoparathyroidism rate of 4.74%. Factors affecting the development of transient hypocalcemia were found as being operated for hyperthyroidism, and use of total thyroidectomy as the surgical method. Total thyroidectomy increased the risk of postoperative hypocalcemia by 3.16 fold. Patients undergoing operations for hyperthyroidism had a 2.3 fold increase, and those undergoing total thyroidectomy had a 3.16 fold risk of postoperative hypocalcemia.

CONCLUSION

Hyperthyroidism surgery and total thyroidectomy lead to a higher risk of developing early postoperative or transient hypocalcemia. According to our results, no significant relationship could be established between any of the study parameters and persistent hypocalcemia.