A common single-nucleotide polymorphism of BRCA2 is associated with severe oligospermia.Men with mild oligospermia (semen concentration of 15 million to 20 million sperm/ml) were studied for an association of sperm DNA damage with life style factors. A significant association was found between sperm DNA damage and factors such as age, obesity and occupational stress. Treatment
Treatment takes place within the context of infertility management and needs also to consider the fecundity of the female partner. Thus the choices can be complex. In a number of situations direct medical or surgical intervention can improve the sperm concentration, examples are use of FSH  in men with pituitary hypogonadism, antibiotics in case of infections,  or operative corrections of a hydrocele, varicocele, or vas deferens obstruction. In most cases of oligospermia including its idiopathic form there is no direct medical or surgical intervention agreed to be effective. Empirically many medical approaches have been tried including clomiphene citrate, tamoxifen, HMG, FSH,  HCG, testosterone, Vitamin E, Vitamin C, anti-oxidants, carnitine, acetyl-L-carnitine, zinc, high-protein diets. In a number of pilot studies some positive results have been obtained. Clomiphene citrate has been used with modest success. The combination of tamoxifen plus testosterone was reported to improve the sperm situation.The use of carnitine showed some promise in a controlled trial in selected cases of male infertility improving sperm quality and further studies are needed.In many situations, intrauterine inseminations are performed with success.
Factor XIII or fibrin stabilizing factor is a zymogen found in blood of humans and some other animals. It is activated by thrombin to factor XIIIa. Factor XIIIa is an enzyme of the blood coagulation system that crosslinks fibrin. Deficiency of XIII worsens clot stability and increases bleeding tendency.Human XIII is a heterotetramer. It consists of 2 enzymatic A peptides and 2 non-enzymatic B peptides. XIIIa is a dimer of activated A peptides. Function
Within blood, thrombins cleave fibrinogens to fibrins during coagulation and a fibrin-based blood clot forms. Factor XIII is a transglutaminase that circulates in human blood as a heterotetramer of two A and two B subunits. Factor XIII binds to the clot via their B units. In the presence of fibrins, thrombin efficiently cleaves the R37–G38 peptide bond of each A unit within a XIII tetramer. A units release their N-terminal activation peptides.Both of the non-covalently bound B units are now able to dissociate from the tetramer with the help of calcium ions (Ca2+) in the blood; these ions also activate the remaining dimer of two A units via a conformational change.Factor XIIIa (dimer of two active A units) crosslinks fibrins within the clot by forming isopeptide bonds between various glutamines and lysines of the fibrins. These bonds make the clot physically more durable  and protect it from premature enzymatic degradation (fibrinolysis).In humans, plasmin, antithrombin and TFPI are the most relevant proteolytic inhibitors of the active factor XIIIa. α2-macroglobulin is a significant non-proteolytic inhibitor.