Endocrine and reproductive disorders
The genetics of diabetes mellitus provides a paradigm for the role of genetic factors in common disorders of complex determination. Type II diabetes is an exceptionally common disorder that shows extreme geographical variation but is continuing to increase in prevalence with the trend to higher body mass index levels in many populations. Acromegaly and related disorders of pituitary hypersecretion are mostly sporadic but may form part of the autosomal dominant type 1 multiple endocrine neoplasia. A heterogeneous group of proportionate growth failure, most often from intrauterine life, remains after endocrine causes have been excluded. Most chromosomal disorders impair growth, but specific causes to be considered include Russell-Silver syndrome and Seckel syndrome. Gorlin syndrome, Simpson-Golabi-Behmel syndrome, the PTEN-related disorder Cowden syndrome and the fragile X syndrome Fragile X syndrome type A may be associated with macrocephaly and overgrowth. Genetic counselling in this area must rest on a well-defined diagnostic assessment that integrates clinical assessment with endocrinological and genetic investigations as appropriate.