There was a resurgence of interest in the "HCG diet" following promotion by Kevin Trudeau, who was banned  from making HCG diet weight-loss claims by the U.S. Federal Trade Commission in 2008, and eventually jailed over such claims.A 1976 study in the American Journal of Clinical Nutrition concluded that HCG is not more effective as a weight-loss aid than dietary restriction alone.A 1995 meta analysis found that studies supporting HCG for weight loss were of poor methodological quality and concluded that "there is no scientific evidence that HCG is effective in the treatment of obesity; it does not bring about weight-loss or fat-redistribution, nor does it reduce hunger or induce a feeling of well-being".On November 15, 2016, the American Medical Association (AMA) passed policy that "The use of human chorionic gonadotropin (HCG) for weight loss is inappropriate." There is no scientific evidence that HCG is effective in the treatment of obesity. The meta-analysis found insufficient evidence supporting the claims that HCG is effective in altering fat-distribution, hunger reduction, or in inducing a feeling of well-being. The authors stated "…the use of HCG should be regarded as an inappropriate therapy for weight reduction…" In the authors opinion, "Pharmacists and physicians should be alert on the use of HCG for Simeons therapy. The results of this meta-analysis support a firm standpoint against this improper indication. Restraints on physicians practicing this therapy can be based on our findings."
These dimers and monomers are not known to participate in coagulation, whereas the tetramers do.A units have a mass of about 83 kDa, 731 amino acid residues, 5 protein domains (listed from the N-terminal to C-terminal, residue numbers are in brackets):
activation peptide (1–37)
β-sandwich (38–184)
catalytic domain (185–515), in which the residues C314, H373, D396 and W279 partake in catalysis
β-barrel 1 (516–628)
β-barrel 2 (629–731)B units are glycoproteins. Each has a mass of about 80 kDa (8.5% of the mass is from carbohydrates), 641 residues and 10 sushi domains. Each domain has about 60 residues and 2 internal disulfide bonds. Physiology
A subunits of human factor XIII are made primarily by platelets and other cells of bone marrow origin. B subunits are secreted into blood by hepatocytes. A and B units combine within blood to form heterotetramers of two A units and two B units. Blood plasma concentration of the heterotetramers is 14–48 mg/L and half-life is 9–14 days.A clot that has not been stabilized by FXIIIa is soluble in 5 mol/L urea, while a stabilized clot is resistant to this phenomenon. Factor XIII deficiency
Deficiency of Factor XIII (FXIIID), while generally rare, does occur, with Iran having the highest global incidence of the disorder with 473 cases. The city of Khash, located in Sistan and Balochistan provinces, has the highest incidence in Iran, with a high rate of consanguineous marriage. Diagnostic use
Factor XIII levels are not measured routinely, but may be considered in patients with an unexplained bleeding tendency.