Why Are LH and FSH High With Low Testosterone in 46,XX DSD?

When your blood tests show high luteinizing hormone (LH) and follicle-stimulating hormone (FSH) alongside low testosterone, it means your brain and testicles are in a mismatched conversation. Your brain senses that your body does not have enough testosterone. In response, it pumps out extra LH and FSH—the messenger hormones that tell the testicles to work harder ^[1][2]. However, because of the way testicles develop in 46,XX testicular difference of sex development (DSD), they may have limited ability to produce enough testosterone to meet the demand. Doctors refer to this condition as hypergonadotropic hypogonadism ^[1]—meaning the signaling hormones are high (hypergonadotropic) while testicular hormone production is low (hypogonadism).

The Hormone Feedback Loop

To understand why your levels are off, it helps to look at the normal communication loop between your brain and your reproductive system:

• The Command Center (Hypothalamus and Pituitary): A part of your brain called the hypothalamus releases signals in rhythmic pulses. These pulses tell the pituitary gland to release LH and FSH into your bloodstream ^[3].
• The Messengers (LH and FSH): LH travels to the testicles and tells the Leydig cells to produce testosterone ^[4]. Meanwhile, FSH tells the Sertoli cells to support healthy tissue development, assist in sperm production, and produce a hormone called inhibin B ^[5].
• The Feedback Signal: When testosterone and inhibin B levels rise to normal amounts, they send a feedback signal back to the brain. Testosterone primarily tells the brain to slow down LH production, while inhibin B provides a selective signal to slow down FSH production ^[6][5].

When the testicles cannot produce enough testosterone or inhibin B, that feedback signal is weaker. Without this braking mechanism, the brain continues to release high levels of LH and FSH to try to stimulate the testicles ^[6][5].

Why This Happens in 46,XX Testicular DSD

In 46,XX testicular DSD, the testicles form differently during fetal development. For many people, a piece of genetic material from the Y chromosome (often the SRY gene) triggers testicular development despite the presence of XX chromosomes ^[7]. In others without the SRY gene, different genetic pathways (such as changes in genes like SOX9) lead to testicular development ^[8].

While testicular tissue does form, its internal structure operates differently ^[1]. Because of these differences, the Leydig cells may produce lower amounts of testosterone over time ^[1]. At the same time, the Sertoli cells may not produce enough inhibin B ^[5]. The combination of low testosterone and low inhibin B leaves the brain’s LH and FSH production elevated ^[7][2].

This laboratory pattern is commonly seen in 46,XX testicular DSD, but it is not inevitable. In one research study looking at a specific group of patients, elevated FSH was found in about 95% of individuals and elevated LH in about 93%, with 63% showing low testosterone ^[2]. However, hormone levels can fluctuate depending on your age and stage of life; for example, testosterone levels can sometimes be within a normal range during adolescence even while LH and FSH remain high ^[9].

Fertility and 46,XX Testicular DSD

Because 46,XX testicular tissue usually lacks the specific Y-chromosome genes needed for normal sperm production (spermatogenesis), fertility is usually severely impaired, and sperm may be absent (azoospermia) ^[10][11]. High FSH levels specifically reflect this impaired Sertoli cell and sperm-producing function ^[4]. If you have questions about fertility or building a family, it is important to discuss these goals with a reproductive specialist. A new DSD diagnosis and questions about hormones, body changes, and fertility can be emotionally difficult, and an endocrinologist or multidisciplinary DSD team can provide valuable support.

What Does This Mean for Your Care?

Confirming Your Results

A single abnormal lab panel usually requires confirmation. Your doctor will likely want to interpret your results using reference ranges specific to your age and pubertal stage ^[12]. They will typically request one or two follow-up blood tests taken early in the morning, when testosterone levels are naturally highest ^[12].

If you take high doses of the supplement biotin, it can interfere with certain laboratory assays, potentially causing falsely high or low readings depending on the test used ^[13]. A standard multivitamin may not have the same effect, but it is critical to always tell your doctor and the laboratory about all supplements and medications you take. They can determine if you need to pause them before testing.

Considering Testosterone Therapy

If your tests confirm low testosterone, your doctor will evaluate whether you are experiencing symptoms like fatigue, low libido, reduced muscle mass, or mood changes—though these symptoms can also have causes other than hormones. Depending on your age and health goals (such as supporting bone health, sexual function, and personal gender-related goals), you and your endocrinologist may discuss starting testosterone replacement therapy.

If you start testosterone therapy, the medication will provide the missing feedback signal to your brain, which will usually cause your LH and FSH levels to drop ^[6]. This drop means the medication is working to supply the hormone your body needs, not that your testicles have recovered their ability to produce it. You should never start, change, or stop hormone therapy without consulting your doctor, as they will need to monitor your progress, bone health, and potential side effects like increases in your red blood cell count (hematocrit).