Beschwerdebild und Lebensqualität bei Hypoparathyreoidismus anhand eines neu entwickelten Fragebogens

Abstract

Hypoparathyroidism is a rare endocrine disease characterized by low serum calcium levels due to inappropriately low levels of parathyroid hormone (PTH). Patients suffer from a variety of symptoms and complications which causes are not fully elucidated yet. Aim of this study was to develop and employ a disease-specific Hypoparathyroidism questionnaire in order to investigate and quantify hypoparathyorid patients’ complaints and contributing factors. An analytical-empirical approach for construction of the new HPQ 40 - Hypoparathyroid patient questionnaire was used based on retrospective analysis of well-established but non-disease-specific questionnaires (e.g. Short-Form-36 Health Survey) in a German hypoparathyroidism self-help group (n = 33/ n=27). This questionnaire was administered prospectively (n=151) in patients with postsurgical Hypoparathyroidism (HypoPT) and two different control groups (patients having undergone thyroid surgery without hypoparathyroidism [=ThySu] and patients with primary hyperparathyroidism [=pHPT]). Exploratory factor analysis revealed five areas of complaint (scales), of which the scales pain and cramps (5 items, Cronbachs α = 0.809), depression and anxiety (5 items, α = 0.860) and loss of vitality (6 Items, α = 0.885) were further investigated. Prospective testing was conducted in 49 HypoPT patients matched for gender and age with 39 ThySu and 35 pHPT patients. As expected, significant group differences were found for albumin-corrected serum calcium, phosphate, PTH and calcium-phosphate product (in all cases: p < 0.001). The initial version of the loss of vitality scale didn’t capture quality of life adequately (p = 0.121-0.095) and was therefore revised. In contrast to the retrospective analysis, the depression and anxiety scale (p = 0.338) and depression screening questions revealed no significant differences between groups (p = 0.167). A higher occurrence of lung diseases or osteoporosis (p = 0.041/ p = 0.026) in one or both control groups may have affected these results. Pain and cramps were newly identified as a relevant area of complaint with HypoPT patients showing significantly higher scores on this scale compared with both control groups (ThySu: p=0.001; pHPT: p = 0.003). The pathophysiology of muscular complaints as well as pain may be explained by underlying parathyroid hormone deficiency. Previous investigations probably underestimated the impact of these complaints. Additional potential relations between the patients’ complaints and PTH (correlation: p<0.05), calcium-phosphate product (p<0.05) and thiazide intake (p<0.05) were found. Besides there were indications for the influence of calcium- (p < 0.001) und magnesium-(p < 0.05) and alfacalcidol- intake (correlation: p < 0.05; group difference: p = 0.002). Calcium-Phosphate deposition in the muscle, serum fluctuations of electrolytes or transient hypercalcemia may be causative. Besides alternative, direct effects of alfacalcidol are possible. With respect to psychometric test criteria reliability (measured with Cronbach’s alpha) was >0.7 for all scales. The analytical-empirical methods as well as expert review further contributed to validity. Further validation and standardization of the questionnaire should be performed in consideration of the influence of medication. The HPQ 40 fulfills basic requirements such as practicability, feasibility, and low administrative burden and can be implemented in future studies as well as in daily practice to gain new insight on hypoparathyroidism.