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Commentary to the Article—Low Levels of Sex Hormone-Binding Globulin and Testosterone Are Associated with Smaller, Denser Low Density Lipoproteins in Normoglycemic Men^c

University Hospital De Pintelaan 185 Gent, Belgium

In the study by Haffner et al. (1), published a few months ago, the authors give some very surprising data on hormonal levels.

Mean testosterone levels in this group of normal middle-aged men is reported to be 5.6 nmol/L with a range of 1.8–33.1 nmol/L. In all publications concerning testosterone levels in normal males, 10 nmol/L is considered the lower normal limit. It is hardly believable that a man with 1.8 nmol/L (= ± 50 ng/dL) testosterone would not be hypo-gonadal.

Even more surprising are the data for free testosterone, reported to be 17.1 pmol/L or ± 3 pro mille total testosterone. Again all data in the literature consider 1–2% of total T to be nonproteinbound, and 5 ng/dL is generally considered the lower normal limit of FT. As to the SHBG binding capacity in these normal subjects, this is reported to vary between 1.4 and 104 nmol/L. Again, 1.4 nmol/L is well below the normal level—it corresponds to a binding capacity of T of 40 ng/dL; in other words, a man with a normal testosterone concentration of 20 nmol/L would have almost all his testosterone either bound to albumin or free (the latter about 1 nmol/L!). Applying the law of mass action to the interaction of T with plasma proteins using the FT values reported in this paper will yield SHBG binding capacities that are several times higher than the values reported here (2).

Finally, mean DHEAS levels are reported to be 175 µmol/L or ± 50 mg/L. These figure are not printing errors, as one could imagine, as they repeated in Table 1 and Table 3 of the article by Haffner et al (1).

In the view of these unusual hormonal data, one doubts the validity of the conclusion concerning a relationship between levels of SHBG and testosterone, respectively, with smaller, denser low density lipoproteins in normoglycemic men.

Note from the Editors

The corresponding author of the subject article of this letter received a copy of the letter but, after multiple requests, declined to respond to it.

Footnotes

Address correspondence to: Dr. Alex Vermeulen, Department of Endocrinology and Metabolism, University Hospital, De Pintelaan 185, Gent, Belgium 9000.

Received September 8, 1997.

References

1. Haffner SM, Laakso M, Miettinen H, Mykkänen L, Karhapää P, Rainwater DL. 1996 Low Levels of Sex Hormone-Binding Globulin and Testosterone Are Associated with Smaller, Denser Low Density Lipoprotein in Normoglycemic Men. J Clin Endocrinol Metab. 81:3697–3701.[Abstract]
2. Rosner W. 1997 Errors in the Measurement of Plasma Free Testosterone (Letter). J Clin Endocrinol Metab. 82:2014–2015.[Free Full Text]

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