Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

SHBG
9285
and to define the allergens responsible for eliciting signs and symptoms. Testing also may be useful to
identify allergens which may be responsible for allergic disease and/or anaphylactic episode, to confirm
sensitization to particular allergens prior to beginning immunotherapy, and to investigate the specificity
of allergic reactions to insect venom allergens, drugs, or chemical allergens.
Interpretation: Detection of IgE antibodies in serum (Class 1 or greater) indicates an increased
likelihood of allergic disease as opposed to other etiologies and defines the allergens that may be
responsible for eliciting signs and symptoms. The level of IgE antibodies in serum varies directly with the
concentration of IgE antibodies expressed as a class score or kU/L.
Reference Values:
Class IgE kU/L Interpretation
0 Negative
1 0.35-0.69 Equivocal
2 0.70-3.49 Positive
3 3.50-17.4 Positive
4 17.5-49.9 Strongly positive
5 50.0-99.9 Strongly positive
6 > or =100 Strongly positive Reference values
apply to all ages.
Clinical References: Homburger HA: Allergic diseases. In Clinical Diagnosis and Management by
Laboratory Methods. 21st edition. Edited by RA McPherson, MR Pincus. New York, WB Saunders
Company, 2007, Chapter 53, Part VI, pp 961-971
Sex Hormone-Binding Globulin (SHBG), Serum
Clinical Information: Sex hormone-binding globulin (SHBG), a homodimeric 90,000 to 100,000
molecular weight glycoprotein, is synthesized in the liver. Metabolic clearance of SHBG is biphasic, with
a fast initial distribution from vascular compartment into extracellular space (half-life of a few hours),
followed by a slower degradation phase (half-life of several days). SHBG binds sex steroids with high
affinity (KD approximately 10[-10]M), dihydrotestosterone (DHT) ->testosterone (T) ->estrone/estradiol
(E). Although each monomeric subunit contains 1 steroid binding site, the dimer tends to bind only a
single sex-steroid molecule. The main function of SHBG is sex-steroid transport within the blood stream
and to extravascular target tissues. SHBG also plays a key role in regulating bioavailable sex-steroid
concentrations through competition of sex steroids for available binding sites and fluctuations in SHBG
concentrations. Because of the higher affinity of SHBG for DHT and T, compared to E, SHBG also has
profound effects on the balance between bioavailable androgens and estrogens. Increased SHBG levels
may be associated with symptoms and signs of hypogonadism in men, while decreased levels can result in
androgenization in women. SHBG levels in prepubertal children are higher than in adults. With the
increase in fat mass during early puberty they begin to fall, a process that accelerates as androgen levels
rise. Men have lower levels compared with women and nutritional status is inversely correlated with
SHBG levels throughout life, possibly mediated by insulin resistance. Insulin resistance, even without
obesity, results in lower SHBG levels. This is associated with increased intra-abdominal fat deposition
and an unfavorable cardiovascular risk profile. In postmenopausal women, it may also predict the future
development of type 2 diabetes mellitus. Androgens and norethisterone-related synthetic progesterones
also decrease SHBG in women. Endogenous or exogenous thyroid hormones or estrogens increase SHBG
levels. In men, there is also an age-related gradual rise, possibly secondary to the mild age-related fall in
testosterone production. This process can result in bioavailable testosterone levels that are much lower
than would be expected based on total testosterone measurements alone.
Useful For: Diagnosis and follow-up of women with symptoms or signs of androgen excess (eg,
polycystic ovarian syndrome and idiopathic hirsutism) An adjunct in monitoring sex-steroid and
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