Spontaneous remission of recurrent secondary hyperparathyroidism ...

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Spontaneous remission of recurrent secondary hyperparathyroidism Sir, Spontaneous necrosis of a parathyroid gland is a rare complication that has been described in a few cases of primary [1–3] and secondary hyperparathyroidism [4]. We present a case of parathyroid necrosis which occurred in recurrent secondary hyperparathyroidism following parathyroidectomy. Case. A 71-year-old man with secondary hyperparathyroidism was referred to our clinic for parathyroidectomy. He had been on haemodialysis since 1991 because of chronic renal failure due to polycystic kidney disease. Other relevant data of his past medical history included multiple vascular access thromboses due to protein C deficit, for which he was administered warafarin, and previous parathyroidectomy of four glands in 1994. On that occasion, the histology of the glands showed nodular hyperplasia, and the total weight of the excised glands was 3.6 g. During the postoperative period he developed hungry bone syndrome and required significant amounts of intravenous and oral calcium supplementation. His Parathyroid hormone (PTH ) levels immediately after parathyroidectomy were 5 pmol/l. PTH levels gradually increased over the next 4 years despite treatment with calcitriol and phosphorus binding agents. When medical treatment was no longer efficacious (PTH 150 pmol/l, Ca 9 mg/dl, P 6.3 mg/dl ), he was referred to us for evaluation. This was interpreted as recurrence of his hyperparathyroidism due to the development of an ectopic gland or an embryonic remmant, and parathyroidectomy was indicated. Prior to parathyroidectomy, new PTH, Ca and P levels were determined for close biochemical monitoring before and after surgery. Surprisingly, the results were inconsistent with the diagnosis of recurrent hyperparathyroidism (PTH 2.8 pmol/l, Ca 7.4 mg/dl, P 3.5 mg/dl ) and consistent with hungry bone syndrome. Partial necrosis of the parathyroid gland was suspected and parathyroidectomy was subsequently cancelled. The patient initially required significant amounts of calcium and calcitriol supplements in order to keep his Ca levels within normal limits. However, 4 months later his calcium and phosphorus levels were easily controlled with calcium carbonate (3 g daily). At the last analysis PTH levels were 8.5 pmol/l, Ca 10 mg/dl, and P 5 mg/dl. Comment. Spontaneus necrosis of a hyperplastic parathyroid gland or parathyroid adenoma is a rare event. There are only a few cases described in the literature; most of them in primary [1–3], but also a few in secondary hyperparathyroidism [4]. However, our case is the first one in which necrosis occurred in recurrent hyperparathyroidism due to growth of an ectopic gland. The clinical consequences of autoparathyroidectomy vary in presentation and in severity. In some cases, the diagnosis was established because the patient complained of local symptoms (pain, dysphagia, or presence of a swollen lump in the anterior neck) and there were initial increases in PTH and calcium because of swelling of the gland previous to the necrosis which could have caused a transient rise in hormone release. In one case, this caused fatal hypercalcaemia [5]. This stage was usually followed by hypocalcaemia because of the hungry bone syndrome once the necrosis had been established. Other cases presented with mild to severe hypocalcaemia, with symptoms of overt or latent tetany. The latter could be due to a delayed diagnosis, occurring after the hypercalcaemic period, or to the absence of this hyper-

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calcaemic period if significant swelling did not precede the necrosis of the gland. It is very unlikely that our patient had a hypercalcaemic period since the careful biochemical monitoring and absence of symptoms almost exclude it. An interesting question is the potential role of anticoagulation or hypercoagulability. Previous reports have pointed to a possible involvement of heparin in the development of haemorrhage. We do not think anticoagulation plays a primary role in this situation. First, the change of the clotting time induced by the heparinization used for haemodialysis is not important enough to cause bleeding provided there is no local problem. Secondly, although the anticoagulation therapy in our patient consisted of warfarin in addition to the heparin used for dialysis, there was no evidence of haemorrhage preceding the necrosis of the gland. Therefore, we think that the primary event is gland infarction, and following that, anticoagulation may predispose to secondary haemorrhage. The co-existence of focal necrosis and anticoagulation may favour haemorrhagic events in the parathyroid gland and thereby lead to its destruction, especially in cases of permanent anticoagulation. This may not occur to the same extent in patients who are not on permanent anti-coagulation, or who have no permanent anti-coagulation problems, such as the protein C deficiency of our patient. As necrosis of the parathyroid gland is an uncommon complication, the management of it is not well defined. Although some authors have recommended removal of the remaining parathyroid tissue when haemorrhage is extensive because of potential recurrence [1], we do not support a generalized recommendation. In our patient there were no serious haemorrhagic or metabolic complications. An unnecessary parathyroidectomy would have led to hypoparathyroidism. Four months later, serum Ca, P and PTH levels were well controlled with medical treatment, and there were no local complications. His hyperparathyroidism may recur in the future, but for the moment conservative management is preferred, although careful monitoring is mandatory in such cases. Nephrology Service Hospital Universitari Arnau de Vilanova Lleida Spain

M. P. Marco S. Muray E. Ferna´ndez

1. Natsui K, Tanaka K, Suda M, Yasoda A, Yonemitsu S, Nakao K. Spontaneous remission of primary hyperparathyroidism due to hemorrhagic infarction in the parathyroid adenoma. Intern Med 1996; 35: 646–649 2. Kovacs KA, Gay JDL. Remission of primary hyperparathyroidism due to spontaneous infarction of a parathyroid adenoma. Medicine 1998; 77: 398–402 3. Hotes LS, Barzilay J, Cloud LP, Rolla AR. Spontaneous hematoma of a parathyroid adenoma. Am J Med Sci 1989; 297: 331–333 4. Hammes M, DeMory A, Sprague SM. Hypocalcemia in endstage renal disease: a consequence of spontaneous parathyroid gland infarction. Am J Kidney Dis 1994; 24: 519–522 5. Dowlatabadi H. Acute fatal parathyroid poisoning associated with necrosis of the parathyroid adenoma prior to death. J Clin Endocrinol Metab 1959; 19: 1481–1485

Indinavir pharmacokinetics in haemodialysis Sir, Indinavir is a potent HIV-1 protease inhibitor which is frequently used as part of highly active antiretroviral therapy regimen. Since 10–20% of the dose is recovered in the urine as parent compound, it has been suggested that kidney