Familial clustering of a disease is an indicator of a possible heritable cause. In the era of genome scans, the consideration of data on heritability should be important in the assessment of the likely success of the scans.
The objective of the study was to carry out a family study on nonthyroid endocrine diseases to search familial clustering of these diseases beyond the known syndromes.
The Swedish Multigeneration Register on 0- to 72-yr-old subjects was linked to the Hospital Discharge Register from years 1964 to 2004.
Standardized incidence ratios were calculated for offspring of affected parents and siblings by comparing with those whose relatives had no hospitalization for nonthyroid endocrine diseases.
A total of 11,948 hospitalized cases and 443 familial cases were identified. The familial standardized incidence ratios were increased for parathyroid, pituitary, and adrenal hyperfunctions and hypofunctions, some findings consistent with known syndromes, most clearly that for adrenal cortical hypofunction showing recessive inheritance described for autoimmune polyendocrine syndrome 1. The sibling risks were very high for many diseases, but some of these affecting young individual may be due to bias caused by selective hospitalization. A high sibling risk observed for anterior pituitary hypofunction may represent a yet-unknown recessive syndrome.
To our knowledge this is a first population-based study on nonthyroid endocrine diseases. The results call for further studies to sort out the challengingly high sibling risk for many individual nonthyroid endocrine diseases, whether they are due to bias or possible recessive effects.