Why is it important to test for SHBG?
Sex hormone binding globulin (SHBG) can be a helpful marker for determining insulin resistance and/or sleep apnea. SHBG is one of the most misunderstood, underutilized and underrated health markers in medicine. We would like to help increase awareness of the SHBG blood test as well as provide a simplified explanation of the role SHBG plays in the body and why you need to be concerned when these levels get too low (or too high, as we will cover this in another blog post).
What is SHBG and what does it do?
SHBG is a protein substance manufactured in the liver that is responsible in the transportation of sex hormones testosterone, dihydrotestosterone and estradiol. SHBG helps keep our sex hormones in balance.
What causes low SHBG?
It is difficult to tell what causes low SHBG, but there are established associated diseases that may give your clinician clues. Articles from the Mayo Clinical Laboratories and the Biology of Reproduction point to the following associated conditions and diseases:
- Insulin Resistance
- Type 2 Diabetes
- Sleep Apnea
- Metabolic Syndrome
- Lipid abnormalities
- High Blood Pressure
Our clinical experience with SHBG
In working with our patients/clients on preventative health issues, we will have them bring in any prior blood work. Often times we have noticed that CBC and lipid panels show slightly elevated fasting glucose scores (above 100), borderline pre-diabetic levels (around 5.6) and lipid abnormalities (High triglycerides and elevated LDL) . In this scenario, the patient works with us to help clean up the diet and lifestyle to improve blood sugar and normalize lipids to prevent having to go on medications. If the patient/client does his/her due diligence and those numbers do not improve, we have found that it is important to further investigate why this is happening.
Our priority in this scenario is to find out why the sugars are not improving. We believe that testing SHBG levels along with a comprehensive hormone panel, ruling out sleep apnea (via sleep study) and testing fasting insulin is underutilized and is a common roadblock for those trying to control their blood sugar and prevent diabetes. If underlying causes are not explored there is no chance for preventative intervention. For example, if someone was unaware they had sleep apnea for several years; it could play a role in triggering diabetes.
According a recent article in Pubmed: “Recent reports have indicated that the majority of patients with type 2 diabetes also have obstructive sleep apnea (OSA). There is compelling evidence that OSA is a significant risk factor for cardiovascular disease and mortality. Rapidly accumulating data from both epidemiologic and clinical studies suggest that OSA is also independently associated with alterations in glucose metabolism and places patients at an increased risk of the development of type 2 diabetes.”
If sleep apnea is detected early, diabetes and many other cardiovascular conditions may be prevented, or at least partially prevented.
Another example of preventative intervention would be to test for fasting insulin levels. Many times patients whom have slightly elevated fasting glucose and hemoglobin A1C are told to “watch their diets and reduce sugar and carbohydrate intake”. In our clinic if fasting insulin levels are elevated, our patients/clients are strongly advised to eliminate all grains, starchy carbs and sugars. Increased fasting insulin levels may suggest the beginning of insulin resistance. If those who have established higher fasting insulin levels do not eliminate sugars and refined carbs, the chances of developing type 2 diabetes is a real possibility.
We suggest including the following tests when SHBG is low:
- Fasting Insulin
Fasting insulin is a relevant test because increased insulin levels prevent the liver from producing SHBG. The majority of SHBG is produced in the liver.
- Thyroid stimulating hormone (TSH)
TSH is an important blood test to perform because low TSH levels can cause low SHBG.
- Free Testosterone
Getting a look at all hormones in the body can help a clinician troubleshoot reasons why SHBG levels may be influenced or are influencing other hormones in the body.
- Sleep Study
We recommend the patient/client to visit a sleep lab and have a sleep study completed.
If you have made diet, exercise and lifestyle modifications and your blood sugar numbers are not optimal (high normal or pre-diabetic), have your doctor or some health care practitioner expand blood testing to see if there are other things blocking your progress.
New England Journal of Medicine: Eric L. Ding, Sc.D., Yiqing Song, M.D., Sc.D., JoAnn E. Manson, M.D., Dr.P.H., David J. Hunter, M.B., B.S., Sc.D., Cathy C. Lee, M.D., Nader Rifai, Ph.D., Julie E. Buring, Sc.D., J. Michael Gaziano, M.D., M.P.H., and Simin Liu, M.D., Sc.D.
N Engl J Med 2009; 361:1152-1163 September 17, 2009DOI: 10.1056/NEJMoa0804381
J Clin Endocrinol Metab. 1989 Feb;68(2):352-8.
Neuroendocrine dysfunction in sleep apnea: reversal by continuous positive airways pressure therapy.
Mayo Clinical Laboratories
1. Pugeat M, Crave JC, Tourniare J, Forest MG: Clinical utility of sex hormone-binding globulin measurement. Horm Res 1996;45:148-155
2. Tehernof A, Despres JP: Sex steroid hormone, sex hormone-binding globulin, and obesity in men and women. Horm Metab Res 2000;32:526-536
3. Kahn SM, Hryb DJ, Nakhle AM, Romas NA: Sex hormone-binding globulin is synthesized in target cells. J Endocrinol 2002;175:113-120
4. Hammond GL: Access of reproductive steroids to target issues. Obstet Gynecol Clin North Am 2002;29:411-423
5. Elmlinger MW, Kuhnel W, Ranke MB: Reference ranges for serum concentrations of lutropin (LH), follitropin (FSH), estradiol (E2), prolactin, progesterone, sex hormone binding globulin (SHBG), dehydroepiandrosterone sulfate (DHEA-S), cortisol and ferritin in neonates, children, and young adults. Clin Chem Lab Med 2002;40(11):1151-1160
Biology of Reproduction
Diverse Roles for Sex Hormone-Binding Globulin in Reproduction
↵2Correspondence: Geoffrey L. Hammond, Child & Family Research Institute, 950 West 28th Avenue, Vancouver, BC V5Z 4H4, Canada. FAX: 604 875 2496;