About estrogens effects on men: bone morphology, mineral density and resistance index in two estrogen-deficient male adults

The effects of estrogens on bone tissue in males have not been well established. We had the opportunity to observe several bone parameters in two estrogen deficient men (both were 28 years old). They presented a typical phenotype of a congenital aromatase deficiency. The first patient presented an homozigous mutation of the exon V of the CYP 19 gene from ACG to ACA affecting the splicing of the RNA and associated with an androgen deficiency and a crypthorquidism. He had dolic biotype features in head, mainly due to basal jaw development. Mid-shaft cortical area (Act), cross sectionals moments of inertia (CSMI), volumetric bone mineral density (vBMD) and stress-strain indexes (SSI) of bone resistance to deformations were estimated at different sites (tibia, radio, jaw) by tridimensional tomography (XCT 3000- Stratec, Pforzheim). Structural deformations were clearly ob- served at mid-shafts Act; over-normal vBMD values were clearly observed at jaws (from 1255-1355 mg/cm3); threshold analysis showed an irregular distribution of the area with a high bone density (over 700 mg); SSIpolarand SSIx.axis indexes were appar- ently normal but CSMIs were variable. The second patient had a mutation in the exon IV from ATG to AGG, methionine to arginine. But it is an heterozygous mutation of the CYP19 gen. He presented a phenotype of estrogen and aromatase deficiencies. Cephalometrywas over normal value for the race and sex (+3 SD). Specifically, perialveolar, not basals, are preserved. Histomorphometric analysis of transiliac bone biopsy performed after double tetracycline labelling showed a high bone turnover with an active osteoblastic synthesis. The eroded surfaces were 2.7 fold higher than controls, osteoid surfaces and volume were increased by x2.6 and x2.8 respectively. The mineralising surfaces were extended at 21.7 %. There was no mineralization defect. These findings may be explained from different viewpoints, including: 1- Mechanically, bone alterations may correspond to a non-directional modelling and remodelling since born, and cortical changes may be an adaptive mechanism 2- Metabolically, long-term non-hormonal controlled bone turnover may disturb directional modelling and remodelling resulting in deformations. Despite mechanisms, bone quality in these two males without estrogens synthesis is abnormal, although resistance is still acceptable.