Patients with fibromyalgia (FM) also may develop primary hyperparathyroidism (PHP), a disease that shares several symptoms with FM, according to a study by Brazilian researchers.
The study, “High Frequency Of Asymptomatic Hyperparathyroidism In Patients With Fibromyalgia: Random Association Or Misdiagnosis?,” was published in the journal Revista Brasileira de Reumatologia.
PHP is a disease characterized by a hyperactive parathyroid gland (high levels of parathyroid hormone – PTH) and consequent hypercalcemia (high levels of calcium in the blood). The condition affects mostly people older than 50 and post-menopausal women.
The clinical diagnosis of PHP often is difficult because its symptoms are variable and similar to those of fibromyalgia, including musculoskeletal pain, cognitive disorders, insomnia, depression and anxiety.
Most PHP patients have asymptomatic hypercalcemia, which is elevated levels of calcium without the presence of the classic manifestations of PHP. But another form of PHP also can occur, consisting of patients who have normal blood calcium levels and high levels of PTH in the absence of other known cause for this hormonal increase; that is called normocalcemic hyperparathyroidism. It has been proposed this would be the first phase of the disease, starting with elevated PTH only and then developing later into full PHP with high levels of calcium.
“Despite the similarity between symptoms of FM and asymptomatic hyperparathyroidism, there are few publications evaluating this association,” the authors wrote. “This study aimed to determine the frequency of asymptomatic hyperparathyroidism in women with FM, verify the association with clinical parameters, and compare the results of PTH and calcium found in healthy women,” they said.
Researchers evaluated FM symptoms in 100 women with FM (mean age 42.4 years), in comparison with 57 healthy women. At the end of the consultation, a blood sample was collected to analyze levels of calcium and PTH.
The analysis showed that 6% of the FM patients had hypercalcemic PHP, but 17% had only high levels of PTH without high levels of calcium (normocalcemic hyperparathyroidism).
Also, there was no significant association between hyperparathyroidism and FM symptoms, except for epigastric pain, which was more frequent in the group of patients who were diagnosed with both diseases.
“A high frequency of hyperparathyroidism was noted in women with FM versus the general population. Normocalcemic hyperparathyroidism was also more frequent in patients with FM,” the team concluded.
“Normocalcemic hyperparathyroidism should be considered as part of the diagnostic spectrum of hyperparathyroidism, and such patients should be monitored with periodic laboratory determinations, with the aim of an early detection of hypercalcemia,” the authors wrote.
The team considers the results still preliminary and suggests that more studies with larger groups are warranted to confirm the association of the two diseases, and to provide more information about what should be the routine assessment of parathyroid glands in patients with FM.
“Longitudinal studies with greater number of patients are needed to assess whether this is an association by chance only, if the increased serum levels of PTH are part of FM pathophysiology, or even if these would not be cases of FM, but of hyperparathyroidism.” the researchers wrote.