Complete androgen insensitivity Pathophysiology, diagnosis, and management.

The syndrome of complete androgen insensitivity is an X-linked inherited disorder resulting in marked inhibition of androgen action. The following case illustrates a subject with complete androgen insensitivity who, despite being a genetic and gonadal male, presents as a phenotypic female with primary amenorrhea, normal breast development, and lack of axillary and pubic hair. The diagnosis, pathophysiology, and management of the condition are discussed, as well as recently identified abnormalities in the androgen-receptor gene. The partial forms of androgen insensitivity are also included in the discussion.

Luteinizing hormone pulsatility in subjects with 5-alpha-reductase deficiency and decreased dihydrotestosterone production.

The pattern of LH pulsatility in male pseudohermaphrodites with inherited 5 alpha-reductase-2 deficiency (5 alpha RD) and decreased levels of plasma dihydrotestosterone was compared to that in normal males. Analysis of 10-min plasma LH sampling during either a 10- or 24-h period demonstrated that the subjects with 5 alpha RD had 1) a mean plasma LH level, mean LH pulse amplitude, and mean plasma LH nadir that were approximately twice normal; and 2) a mean LH pulse frequency similar to that in normal males, whether described as pulses per h or pulses per study period. An increased plasma LH response to GnRH administration was also noted. The findings suggest that a deficiency of DHT results in decreased negative feedback at the level of the hypothalamus and/or pituitary, resulting in an increase in mean plasma LH, LH pulse amplitude, and LH responsiveness to GnRH. In response to increased LH, mean plasma testosterone (T), free T, and plasma estradiol (E2) are increased. The pulse amplitude is increased despite elevated plasma T and E2 levels; this underscores the importance of DHT in pulse amplitude regulation. LH pulse frequency is not decreased despite elevated plasma T and E2, raising the possibility that DHT deficiency increased pulse frequency that was normalized by increased T and/or E2. In conclusion, studies of LH pulsatility in subjects with 5 alpha RD suggest a role for DHT in the modulation of LH.

A novel mutation in the CAG triplet region of exon 1 of androgen receptor gene causes complete androgen insensitivity syndrome in a large kindred.

Complete androgen insensitivity syndrome (CAIS) is an X-linked inherited disease caused by mutations in the androgen receptor (AR) gene. We have previously reported the largest kindred of CAIS, with 17 46,XY psychosexual and phenotypic females who lack secondary sexual hair. Analysis of AR binding indicated a receptor-negative form of complete androgen insensitivity, and DNA linkage analysis indicated that the absent binding was not caused by a large AR gene deletion. Using PCR-single-strand DNA conformational polymorphism, PCR-denaturing gradient gel electrophoresis, and DNA sequencing, we have identified a novel mutation in the polymorphic CAG trinucleotide region of exon 1 of the AR gene, where a single adenine is inserted, or equivalently, a GC-dinucleotide is deleted at this region of the gene. The mutation results in a frameshift at amino acid 60 and a premature termination of the receptor downstream of the mutation. This predicts a mutant AR with only 79 amino acids in the amino-terminal of AR protein, prohibiting binding to the ligand, as well as the cognate DNA. The rest of the encoding regions of the AR gene in the affected subjects are normal. These results are consistent with previous ligand binding and DNA linkage analysis studies. This new mutation in the CAG trinucleotide area of exon 1 of the AR gene represents the first example of a defect in a CAG repeat causing CAIS in this large kindred. All previous reported variants in this region are changes in the number of triplet repeats.