SHBG (Extended): Which Tests to Order Alongside It and How to Interpret Your Results

What the "Extended" Panel Actually Includes

The standard SHBG test returns one number: the serum concentration of sex hormone binding globulin in nanomoles per liter. The extended version goes further. It uses that SHBG value together with your total testosterone to calculate two additional data points: free testosterone and the free androgen index (FAI).

Free testosterone is the fraction of testosterone not bound to SHBG or albumin, and it is the biologically active portion. Because direct free testosterone assays are technically difficult and poorly standardized across labs, most clinical laboratories calculate it from total testosterone and SHBG using the Vermeulen equation, which has been validated against equilibrium dialysis, the gold-standard method.

The free androgen index is a simpler ratio: (total testosterone in nmol/L divided by SHBG in nmol/L) multiplied by 100. An FAI above 5 in women is generally considered elevated and is commonly used in the workup for hyperandrogenism and PCOS.

Why One Number Is Never Enough

Two women can have identical total testosterone values of 40 ng/dL and completely opposite clinical pictures. If one woman has an SHBG of 30 nmol/L, her free testosterone is relatively high. If the other has an SHBG of 120 nmol/L, most of that testosterone is bound and biologically unavailable. Without SHBG, you cannot interpret testosterone. The same logic applies in reverse: an SHBG reading without testosterone context tells you about the carrier protein but not the hormone cargo.

What SHBG Binds

SHBG binds testosterone with high affinity, dihydrotestosterone (DHT) with even higher affinity, and estradiol with roughly three times lower affinity than testosterone. Estradiol binding to SHBG is clinically relevant in postmenopausal women on hormone therapy, particularly those taking oral estrogen, because oral estrogen substantially raises SHBG production in the liver, altering the free fraction of both estradiol and testosterone simultaneously.

Which Tests to Order Alongside SHBG (Extended)

Ordering SHBG (extended) without a supporting panel is like ordering a single puzzle piece. The tests below transform that single measurement into a clinically actionable picture. Your clinician will select from this list based on your symptoms and life stage, not necessarily order all of them at once.

Core Hormone Panel

Total testosterone. Required. It is the input value for all calculated free testosterone and FAI results. The Endocrine Society clinical practice guideline on testosterone recommends mass spectrometry (LC-MS/MS) over immunoassay for women because female testosterone levels are low and immunoassays lose accuracy in that range. Request LC-MS/MS if your lab offers it.

Estradiol (E2). Adds critical context. High estradiol raises hepatic SHBG production; low estradiol in perimenopause or menopause can be paired with a paradoxically low SHBG if metabolic dysfunction is also present. Order a sensitive estradiol assay (also called E2 ultrasensitive or E2 LC-MS/MS) if you are postmenopausal or prepubertal, where values are below 20 pg/mL and standard immunoassays are unreliable.

LH and FSH. Together these distinguish ovarian failure from hypothalamic suppression, help stage perimenopause, and assist in the PCOS workup where LH:FSH ratios above 2:1 are seen in a substantial proportion of affected women. ACOG recommends FSH as part of the menopause evaluation when clinical staging is uncertain.

DHEA-S. Dehydroepiandrosterone sulfate is an adrenal androgen that does not bind SHBG in significant amounts. Elevated DHEA-S points to adrenal hyperandrogenism rather than ovarian hyperandrogenism, which changes management completely. The Endocrine Society guideline on hyperandrogenism in women specifically recommends DHEA-S as part of the initial androgen screen.

Metabolic Panel

SHBG is synthesized in the liver and is exquisitely sensitive to insulin signaling. High fasting insulin suppresses hepatic SHBG production. This is one of the core mechanisms linking insulin resistance, obesity, and androgen excess in PCOS. A 2010 meta-analysis of 44 studies confirmed an inverse relationship between SHBG and type 2 diabetes risk, with each doubling of SHBG associated with roughly a 70% lower risk of developing diabetes.

Order alongside:

• Fasting insulin and fasting glucose (to calculate HOMA-IR)
• HbA1c if metabolic risk is present
• Fasting lipid panel (low SHBG correlates with atherogenic dyslipidemia)
• Liver function tests if SHBG is unexpectedly low or high, because hepatic disease directly alters production

Thyroid Function

Both hypothyroidism and hyperthyroidism alter SHBG. Hypothyroidism lowers it; hyperthyroidism raises it. TSH should be checked in any woman with unexplained low or high SHBG before attributing the result to metabolic or hormonal causes. Many clinicians also add free T4 if TSH is out of range.

Prolactin

Hyperprolactinemia suppresses GnRH pulsatility, reducing LH and FSH and secondarily lowering sex hormone production. Because it overlaps symptomatically with androgen excess (irregular cycles, low libido), prolactin belongs in the differential whenever SHBG is being ordered as part of a menstrual irregularity or androgen excess workup.

Optional Additions by Indication

| Indication | Add-on test | |---|---| | Suspected 21-hydroxylase deficiency (late-onset CAH) | 17-hydroxyprogesterone (morning, follicular phase) | | Hirsutism workup | Androstenedione | | Fertility evaluation | AMH, Day 3 FSH/E2, progesterone Day 21 | | Postmenopausal bone concern | DXA scan, vitamin D 25-OH, PTH | | Suspected Cushing syndrome | 24-hour urinary free cortisol or 1mg overnight dexamethasone suppression |

Normal SHBG Ranges Across a Woman's Life Stages

Reference ranges for SHBG vary by laboratory, assay method, and life stage. The figures below are derived from the Mayo Clinic Laboratories reference range database and published normative data; always interpret your result against your specific lab's reference interval.

Reproductive Years (Ages 18-40)

The typical range is 18-144 nmol/L, with a wide spread because hormonal contraceptives, body weight, and menstrual cycle phase all shift SHBG. Oral combined contraceptive pills (OCPs) raise SHBG dramatically. In one study, OCPs raised SHBG two- to fourfold compared to non-users, and this elevation can persist for months after stopping the pill, temporarily suppressing free testosterone and sometimes contributing to low libido in the post-pill period.

Perimenopause

Estradiol fluctuates erratically during perimenopause, and SHBG tracks those fluctuations. Because total testosterone also declines with age (roughly 50% lower by the mid-40s compared to peak reproductive levels), even a modest SHBG elevation in this stage can leave free testosterone quite low, contributing to symptoms including low libido, fatigue, and cognitive fog. The Menopause Society (NAMS) position statement on hormone therapy acknowledges free testosterone measurement as useful context in women presenting with low sexual desire.

Postmenopause

Postmenopausal SHBG typically falls in the range of 40-120 nmol/L. Women on oral estrogen therapy will see SHBG climb, sometimes above 150 nmol/L, which may suppress the free fraction of exogenously administered testosterone if that is also part of the regimen. This is one practical reason why transdermal estrogen is preferred over oral estrogen in women who also need testosterone therapy: the transdermal route bypasses first-pass hepatic metabolism and does not raise SHBG to the same extent.

Pregnancy

SHBG rises dramatically during pregnancy due to high estrogen and progesterone stimulating hepatic synthesis. By the third trimester, SHBG concentrations are 5- to 10-fold higher than prepregnancy values. This physiological rise is expected and does not require intervention. It does mean that a postpartum SHBG drawn within the first few weeks after delivery may still reflect pregnancy-level elevations and should not be compared directly to non-pregnant reference ranges.

What High SHBG Means for Women

High SHBG (generally above 144 nmol/L in reproductive-age women, adjusted upward for postmenopausal women on oral estrogen) reduces the bioavailable fractions of both testosterone and estradiol. Symptoms depend on which hormone is most affected.

Common Causes of High SHBG

• Oral estrogen therapy (most common iatrogenic cause)
• Hyperthyroidism
• Liver disease (some forms of hepatitis raise production acutely)
• Eating disorders or severe caloric restriction
• Certain anticonvulsants (phenytoin, carbamazepine)
• Aging (SHBG tends to rise modestly with age independent of hormonal status)

Symptoms Linked to Functionally Low Androgens from High SHBG

Low libido, vaginal dryness, fatigue, and difficulty building muscle mass are the most commonly reported symptoms. These overlap substantially with estrogen deficiency symptoms, which is why the full panel matters. A woman with high SHBG, normal total testosterone, and low free testosterone may have symptoms that look identical to low estrogen.

What Low SHBG Means for Women

Low SHBG (below 18-25 nmol/L in most labs, though cutoffs vary) means more testosterone and estradiol are circulating in the free, biologically active form. The clinical consequences depend heavily on life stage and the absolute hormone levels present.

Common Causes of Low SHBG in Women

• Insulin resistance and hyperinsulinemia (the most common cause in reproductive-age women)
• Obesity, particularly central adiposity
• PCOS
• Hypothyroidism
• Androgen excess (from any source: ovarian, adrenal, or exogenous)
• Glucocorticoid excess (Cushing syndrome or long-term steroid use)
• Progestin-dominant hormonal contraceptives (androgenic progestins such as levonorgestrel lower SHBG more than desogestrel or drospirenone)

SHBG and PCOS

Low SHBG is both a diagnostic marker and a metabolic risk indicator in PCOS. A 2022 systematic review in Fertility and Sterility confirmed that SHBG below 50 nmol/L is seen in approximately 50-70% of women with PCOS and that low SHBG independently predicts insulin resistance even when fasting glucose is normal. The Rotterdam criteria for PCOS do not require SHBG, but the FAI derived from the extended panel has been used in research to quantify androgen excess as an alternative to direct testosterone measurement.

Metabolic Risk Signal

Low SHBG is not just a hormone marker. It appears to be an independent predictor of type 2 diabetes and cardiovascular risk in women. The Nurses' Health Study found that women in the lowest quartile of SHBG had more than twice the risk of developing type 2 diabetes over a 10-year follow-up compared with women in the highest quartile, after adjusting for BMI. This finding positions low SHBG as a metabolic biomarker worth flagging even when androgen symptoms are absent.

How to Raise SHBG Naturally and Medically

If your SHBG is low because of insulin resistance or obesity, the most evidence-based interventions target the underlying driver.

Lifestyle Interventions

Weight loss is the single most effective lifestyle intervention. A 5% reduction in body weight has been shown to raise SHBG significantly in women with obesity and PCOS, alongside improvements in insulin sensitivity. Dietary approaches that lower fasting insulin, including reduced refined carbohydrate intake and increased dietary fiber, also raise SHBG in observational data, though randomized trial data in women specifically are limited. Be aware that crash dieting or very-low-calorie intake can paradoxically lower SHBG in the short term by stressing the liver.

Medical Options

• Metformin: By improving insulin sensitivity, metformin raises SHBG in women with PCOS and insulin resistance. A 2003 Cochrane review found metformin raised SHBG in PCOS, though the magnitude varied across trials.
• Oral estrogen (in perimenopausal or postmenopausal women): Raises SHBG directly by stimulating hepatic synthesis. This is the fastest pharmacologic way to raise SHBG but may not be appropriate if the goal is also to optimize free testosterone.
• Thyroid optimization: Correcting hypothyroidism with levothyroxine raises SHBG as thyroid function normalizes.

How to Lower SHBG

High SHBG is less often the primary treatment target, but it matters clinically when it is suppressing free testosterone or free estradiol to symptomatic levels.

The WomanRx clinical team uses a four-step framework for evaluating whether high SHBG needs direct intervention: (1) confirm the elevation is not assay artifact by repeating with LC-MS/MS if initially run by immunoassay; (2) identify and treat the underlying cause (switch from oral to transdermal estrogen, optimize thyroid, address eating disorder); (3) check whether free testosterone and free estradiol are actually low or just the SHBG is high; (4) consider route-of-administration changes before adding any new agent.

Switching from oral to transdermal estrogen is the most evidence-backed maneuver for lowering iatrogenically elevated SHBG in postmenopausal women. A randomized trial by Shifren et al. demonstrated that transdermal estradiol produced significantly lower SHBG compared with oral estradiol at equivalent clinical doses, with no difference in vasomotor symptom relief.

Danazol and methyltestosterone have been used historically to suppress SHBG but carry significant androgenic side effects and are rarely used for this purpose today in women.

SHBG Across Conditions Specific to Women

PCOS

As described above, low SHBG combined with elevated FAI is a core feature of androgen excess in PCOS. In women trying to conceive who have PCOS, correcting insulin resistance with metformin or lifestyle change may raise SHBG and lower free androgen levels, which can restore ovulatory function in a subset of women.

Endometriosis

The relationship between SHBG and endometriosis is less established than in PCOS. Some research suggests that women with endometriosis have altered androgen metabolism, but SHBG itself has not been shown to be a reliable biomarker for diagnosis or disease severity. Order it as part of a general hormonal evaluation rather than as a disease-specific marker.

Hormonal Acne and Female Pattern Hair Loss

Both conditions involve androgen sensitivity at the receptor level in skin and hair follicles. Free testosterone (derived from the SHBG extended panel) is more useful than total testosterone for assessing androgen-driven acne and female pattern hair loss (androgenic alopecia). An FAI above 5, combined with elevated DHEA-S or androstenedione, points toward an adrenal or ovarian androgen excess that may be driving these symptoms.

Genitourinary Syndrome of Menopause (GSM) and HSDD

In postmenopausal women presenting with vaginal dryness, dyspareunia, or low sexual desire, the SHBG extended panel helps determine whether low free testosterone is a contributing factor. Hypoactive sexual desire disorder (HSDD) has a multifactorial etiology, but free testosterone below the lower quartile of the premenopausal reference range, in the context of elevated SHBG from oral estrogen, is a modifiable contributor. A Menopause Society position statement supports measurement of testosterone levels before initiating testosterone therapy in postmenopausal women with HSDD, though it notes that no FDA-approved testosterone product exists for women in the United States as of 2025.

Osteoporosis

SHBG mediates bone health indirectly. Low estradiol bioavailability (from high SHBG) contributes to bone loss in the early postmenopausal transition. The Study of Women's Health Across the Nation (SWAN) found that SHBG was inversely associated with bone mineral density at multiple skeletal sites in midlife women, independent of total estradiol, suggesting that free hormone availability at bone is clinically relevant.

Evidence Gaps: What We Do Not Know Yet

Women have been systematically underrepresented in the trials that established SHBG reference ranges and clinical cutoffs. Several important gaps remain.

First, most normative SHBG data in women comes from studies that measured SHBG by older immunoassay methods. LC-MS/MS reference ranges for SHBG in women across the full reproductive lifespan are not yet uniformly established, and different labs report different reference intervals.

Second, the clinical cutoff for "low SHBG" in the context of PCOS diagnosis remains debated. No consensus guideline has established a specific nmol/L threshold below which SHBG is diagnostic.

Third, the long-term metabolic significance of SHBG as an independent cardiovascular risk marker in women has not been tested in prospective intervention trials. The associations seen in studies like the Nurses' Health Study are observational and cannot establish that raising SHBG will reduce diabetes or cardiovascular events.

Fourth, SHBG data in transgender women on feminizing hormone therapy and in gender-diverse individuals more broadly is sparse. Clinicians should interpret results in those patients with caution relative to sex-specific reference intervals.

Pregnancy, Postpartum, and Contraception Considerations

SHBG itself is not a drug, so the pregnancy and lactation section here focuses on the hormonal therapies and conditions that interact with SHBG during these stages.

During pregnancy: SHBG rises physiologically and does not require monitoring unless there is a specific clinical concern (for example, suspected androgen-secreting tumor presenting with virilization during pregnancy). No intervention to lower or raise SHBG is appropriate during pregnancy without specialist guidance.

Postpartum: SHBG drops sharply after delivery as estrogen and progesterone fall. In breastfeeding women, prolactin remains elevated and ovarian function is suppressed, keeping estrogen and testosterone low and SHBG correspondingly lower than in cycling women. Symptoms of low libido and vaginal dryness in the postpartum and lactating period often reflect these hormonal shifts rather than a primary SHBG abnormality.

Hormonal contraception: The type of contraceptive pill affects SHBG substantially.

• Combined OCP with ethinyl estradiol raises SHBG two- to fourfold, which may suppress free testosterone and contribute to low libido and low mood in susceptible women. A 2006 Journal of Sexual Medicine study found that SHBG remained elevated for at least 6 months after stopping the pill in a subset of women.
• Progestin-only pills and hormonal IUDs (levonorgestrel) lower SHBG, especially with androgenic progestins, and may worsen androgen-excess symptoms in women with PCOS.
• The etonogestrel implant (Nexplanon) moderately lowers SHBG compared to OCP users.
• If SHBG is being interpreted as part of a PCOS or androgen workup, note the type and duration of any hormonal contraceptive use, because the result will reflect the contraceptive effect on SHBG rather than the underlying endogenous state.

Teratogenic medications: If a woman has been started on medications that affect SHBG, such as anticonvulsants, danazol, or glucocorticoids, and she is of reproductive age, reliable contraception discussions are necessary because several of these agents carry fetal risk. This is the responsibility of the prescribing clinician; SHBG testing itself carries no pregnancy risk.

Who This Panel Is Right For (and Who Can Wait)

Order SHBG Extended If You Have:

• Symptoms of androgen excess: hirsutism, acne, scalp hair thinning, irregular cycles
• PCOS (confirmed or suspected)
• Low libido with normal total testosterone
• Perimenopause or menopause with sexual dysfunction
• Starting or changing hormone therapy (especially switching oral to transdermal)
• Insulin resistance, metabolic syndrome, or type 2 diabetes in context of hormonal symptoms
• Unexplained infertility with suspected hormonal cause

It May Not Be the Right First Step If You Have:

• No hormonal symptoms and are being screened for metabolic risk only (fasting insulin and glucose are more direct)
• Active pregnancy with no specific clinical concern
• Recently started or stopped hormonal contraceptives in the last 3-6 months (results will reflect the drug, not your endogenous status)

Timing the draw matters. For premenopausal women, morning fasting samples in the early follicular phase (days 2-5 of the menstrual cycle) give the most reproducible results for testosterone and SHBG. LH and FSH should also be drawn on days 2-5. The 17-hydroxyprogesterone for CAH exclusion must be drawn in the morning on a follicular phase day as well.

"When ordering SHBG for the purpose of evaluating androgen excess in women, a morning fasting sample during the early follicular phase, paired with total testosterone by LC-MS/MS, DHEA-S, and fasting insulin, provides the most clinically interpretable panel," according to the Endocrine Society Clinical Practice Guideline on Evaluation and Treatment of Hirsutism in Premenopausal Women.