Understanding SHBG and consideration in women with FPHL

SHBG is a sponge for hormones

Many female patients who have had extensive blood tests to evaluate hormone levels and hormone function will often see a test ordered as "Sex hormone binding globulin (SHBG)." SHBG are often ordered for women with irregular periods, acne, women with insulin resistance, some women with severe thyroid abnormalities. Of course, it's sometimes ordered for women with female pattern hair loss 

What is SHBG?

SHBG is a protein that binds to hormones. SHBG binds to androgens and binds to estrogens.  It essentially sops them up and prevents them from doing their job. SHBG levels are higher in women than men and higher before puberty than after puberty. 

Why evaluate SHBG in female pattern hair loss?

In some young women with female androgenetic hair loss, I order SHBG levels. Sometimes I order the tests to gain a better understanding of the diagnosis (see below for causes of low SHBG), but sometimes I order as a means of monitoring as I hope the SHBG levels rise with treatments (such as starting a birth control pills.)

 

Monitoring SHBG is complex and requires expert input as to causes of low and high levels. 

LOW SHBG:

In general, low SHBG levels are seen in women with polycystic ovarian syndrome (PCOS), obesity, insulin resistance and hyperinsulinemia, growth hormone, hypothyroidism, acromegaly, Cushing syndrome (a condition of excessive steroid production by the body), corticosteroids, and use of androgen hormones (testosterone for women), and some types of synthetic progestins (norethindrone, norgestrel, desogestrel, norgestimate)

ELEVATED SHBG:

Many things elevate SHBG including oral contraceptives, estrogens, thyroid problems, liver problems, pregnancy, extreme dieting, cancers, medications (i.e. dilantin), and smoking. In young women, one of the more common causes of increased SHBG is starting oral contraceptives and pregnancy.  Most OCPs lead to an increase in SHBG levels by 3-4 times over baseline. 

COMMENT

Overall, causes of increased and decreased SHBG are sometimes complex and require careful evaluation by a physician knowledgeable about all these causes.