Response to the Letter by Rao S.D., et al

We thank the authors for the interest in our study and for their comments.

In particular, we recognize that the chief limitation of the study, as highlighted by Kulkarni et al, is the small number of patients with estimated glomerular filtration rate (eGFR) less than 60 mL/min. However, that figure represents a 13% percentage in the whole series, which is consistent with recent literature data on the prevalence of renal failure in primary hyperparathyroidism (PHPT) (1).

It is likely that PHPT patients with more advanced stages of renal failure refer to other specialists, such as a nephrologist, thus accounting for the low proportion of this kind of patients in endocrine series.

Regarding the first comment, as correctly deduced from Table 2, the mean duration of follow-up after parathyroidectomy (PTX) was about 2 years without any statistically significant difference between the two evaluated groups. Therefore, even if this 2-year difference in age itself might influence eGFR, we believe that it did not impact differentially on the two groups.

We are aware that the small sample size reduces the statistical power, increasing the chance of a type II error, in particular in the subgroup with an eGFR less than 60 mL/min.

We regret that the key message of our study might have been misunderstood. Actually, we did not want to claim that PTX is not worthwhile in patients with an eGFR greater than 60 mL/min, as for renal protection. On the contrary, we provide the first evidence that PTX may be more advantageous in PHPT patients with an eGFR less than 60 mL/min.

As pointed out by Kulkarni et al, we did not find any link between the major disease indicators and the variations in eGFR before and after PTX. For this reason we did not speculate about PHPT-related pathogenetic factors affecting renal function in both groups.

On the other hand, we recognize, as argued in the literature, that, at least in the less severe form of the disease currently prevalent, the association between PHPT and renal impairment is still controversial.

We agree with the authors that our results should not be used to deny PTX to patients with an eGFR greater than 60 mL/min and that it would have been more appropriate to clarify it in the conclusion paragraph.

Finally, we would like to specify that in the multiple linear regression, the input variable was the baseline eGFR, whereas the outcome was the post-PTX eGFR variation.

Abbreviations

 
• eGFR

  estimated glomerular filtration rate

 
• PHPT

  primary hyperparathyroidism

 
• PTX

  parathyroidectomy.

Reference