Fatigue in Post-surgery Hypoparathyroidism Linked to Problems with Control of Heart Rate, Study Finds

Fatigue in Post-surgery Hypoparathyroidism Linked to Problems with Control of Heart Rate, Study Finds

Greater fatigue in postoperative patients with chronic hypoparathyroidism (hypoPT) is associated with cardiovascular autonomic neuropathy — a neurological impairment in heart rate control, a study suggests.

The study, “Cardiovascular autonomic neuropathy as a cause of fatigue in chronic hypoparathyroidism,” was published in the journal Endocrine.

Hypoparathyroidism is a disorder caused by low levels of the parathyroid hormone (PTH), leading to a pronounced drop in calcium levels in the blood. 

The most common cause (19%–38%) of acquired temporary hypoPT in adults occurs in patients who undergo neck surgery (post-surgical hypoparathyroidism) that injures the parathyroid glands, the structure responsible for producing PTH. Chronic (permanent) hypoPT following a total thyroidectomy — surgically removing the entire thyroid gland — is much more uncommon, less than 3% of all cases.

Despite calcium and vitamin D supplements given to patients to raise these levels in the blood, many with hypoPT report a poor quality of life with symptoms ranging from fatigue, muscle spasms, and pain, to an inability to concentrate, depression, and anxiety. 

“Furthermore, post-surgical chronic hypoPT patients seem to have a twofold increased risk of death … although the causes of this increased mortality are unknown,” the researchers wrote.

Another condition characterized by increased fatigue and a higher mortality risk is cardiovascular autonomic neuropathy (CAN) — a complication seen in people with diabetes. 

CAN is an impairment of the cardiovascular autonomic (automatic) system that controls the heart rate. If can lead to arrhythmia, dizziness, an inability to exercise, abnormal blood pressure, and heart attacks without typical symptoms. 

A recent study found that post-surgical hypoPT was strongly associated with CAN. This prompted researchers to ask if CAN may be the cause of fatigue and a lower quality of life in this patient population.

Researchers recruited 48 patients with post-surgical chronic hypoPT to identify CAN, and to analyze life quality and fatigue scores drawn from patient evaluations. They compared the hypoPT scores to those from 38 surgical patients without calcium disorders, who had surgery to remove a part or all of the thyroid and served as a control group. The average age of all patients was 51.2, and most (91%) were female.

To assess the degree of CAN in a patient, a medical device called the NeuroTester Air — a non-invasive breathing device that measures CAN severity — was applied. 

Quality of life was assessed using the SF-36 Health Survey, a self-reported assessment that analyzes eight factors (dimensions) that influence quality of life. These include bodily pain, general health perception, vitality, mental health, social functioning, role limitations due to emotional functioning, and physical functioning. For each dimension, higher scores reflect better self-reported health.

From these resulting scores, two summary scores were calculated for the physical component summary and the mental component summary.

To assess fatigue, the Functional Assessment of Chronic Illness Therapy (FACIT)-fatigue score was used. The FACIT-fatigue measures an individual’s level of fatigue during daily activities over the past week. Higher scores indicate less fatigue.

Of the 48 hypoPT patients assessed, 10 patients did not have CAN, 19 had early CAN, and confirmed (definite) CAN was identified in another 19 patients. Within this group, no differences were found in age, sex, and levels of calcium, vitamin D, phosphate, PTH, and thyroid-stimulating hormone (TSH). 

A statistical analysis of the scores revealed that post-surgical chronic hypoPT patients had lower (worse) physical component summary and fatigue scores overall compared to the control group. No differences were found in the mental component summary scores and total SF-36 Health Survey scores.

No differences were also seen in the physical component summary, mental component summary, or SF-36 Health Survey scores when comparing hypoPT without CAN to those with early CAN and definite CAN. 

However, post-surgical chronic hypoPT patients with confirmed CAN had significantly lower fatigue scores compared to those without CAN. 

The researchers speculated that “fatigue in hypoPT patients is a result of the inability of the heart to adjust its function to the physical activity level of the subject.”

“CAN may explain fatigue in subjects with chronic post-surgical hypoPT, which is a common complaint of this pathological condition. Further and larger studies are needed to confirm our findings,” the researchers concluded.

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Ana holds a PhD in Immunology from the University of Lisbon and worked as a postdoctoral researcher at Instituto de Medicina Molecular (iMM) in Lisbon, Portugal. She graduated with a BSc in Genetics from the University of Newcastle and received a Masters in Biomolecular Archaeology from the University of Manchester, England. After leaving the lab to pursue a career in Science Communication, she served as the Director of Science Communication at iMM.
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