FSHB rs6170: Understanding This Rare Reproductive Variant
The rs6170 variant is a rare genetic change located within the FSHB gene, which provides instructions for making a subunit of the follicle-stimulating hormone. This specific missense variant, also known as p.Ser20Ile, has been identified in research studies investigating genetic factors associated with spermatogenic impairment in males.
What each genotype means
Typical FSHB variant profile
This genotype represents the most common form of the FSHB gene in many populations. Research suggests that individuals with this genotype may have different responses to fertility treatments compared to those carrying the T allele, but it is not inherently linked to infertility. Please discuss any concerns regarding reproductive health or treatment options with your clinician or fertility specialist.
This is the major allele and is the most common genotype found across global populations.
Heterozygous FSHB variant carrier
Carrying one copy of the T allele may influence how your body produces or responds to follicle-stimulating hormone (FSH). Some studies suggest that this variant can be associated with variations in sperm count or testicular volume, though findings are mixed and often depend on other genetic and environmental factors. You should consult with a reproductive specialist to understand how this might relate to your specific fertility profile.
This genotype is found at varying frequencies depending on ancestry, appearing in a significant minority of individuals in some studied cohorts.
Associated with altered FSH levels
This genotype has been associated in some research with lower serum FSH levels, reduced testicular volume, and lower sperm counts in men experiencing idiopathic infertility. While these associations have been observed in clinical studies, they do not guarantee infertility, as many factors contribute to reproductive health. If you are concerned about fertility, please discuss these results and potential treatment responses with a qualified healthcare provider.
This is a less common genotype, with its prevalence varying significantly across different ethnic and geographic populations.
What is the rs6170 Variant?
The rs6170 variant is a single nucleotide polymorphism (SNP) found in the FSHB gene. In genetics, a missense variant means that the change in the DNA sequence results in a different amino acid being incorporated into the protein structure. Specifically, this variant causes a substitution of serine for isoleucine at position 20 of the FSH-beta protein (p.Ser20Ile). Because this change occurs in the coding region of the gene, researchers investigate whether it alters the function or stability of the resulting hormone. This variant is cataloged in major genetic databases, which track its location and potential impact on human health. It is important to note that identifying a variant does not automatically imply a clinical diagnosis, as many genetic variations are benign and do not cause observable health effects.
The Role of the FSHB Gene
The FSHB gene encodes the beta subunit of follicle-stimulating hormone (FSH). FSH is a critical hormone produced by the pituitary gland that plays a central role in reproductive development and function. In males, FSH is essential for the maturation of Sertoli cells in the testes, which in turn support the process of spermatogenesis—the production of sperm. Because FSH is a key regulator of the reproductive system, variations in the FSHB gene are of significant interest to reproductive biologists and clinicians. When the FSH-beta subunit is altered, it can potentially affect the hormone's ability to bind to its receptor or signal effectively, which may influence testicular volume or sperm production. Understanding how specific variants like rs6170 interact with this biological pathway is a focus of ongoing research into idiopathic male infertility.
Research and Evidence Strength
The evidence linking rs6170 to reproductive health is currently considered moderate. Research, such as studies utilizing next-generation sequencing panels, has identified this variant in cohorts of men presenting with quantitative spermatogenic impairment. In some clinical studies, the prevalence of certain missense variants in the FSHB gene has been observed to be higher in men with abnormal sperm counts compared to those with normal seminal parameters. However, because this variant is rare, large-scale population studies are needed to definitively establish its clinical significance. It is also important to distinguish between statistical associations and direct causation. While a variant may be more common in a specific group, it does not necessarily mean it is the sole cause of a condition. Further functional studies are required to confirm how p.Ser20Ile specifically impacts FSH signaling in the human body.
Population Frequency
The rs6170 variant is classified as a rare variant in the general population. Rare variants are defined by their low minor allele frequency, meaning they are not found in a large percentage of the global population. Because of this rarity, it is difficult to draw broad conclusions about its distribution across different ancestral groups without extensive data. Most research on this variant has been conducted in specific clinical cohorts, such as men attending infertility clinics, rather than in large, unselected population samples. Consequently, the frequency of this variant in the general public remains limited in current databases, and its presence in an individual is an uncommon finding.
What This Information Means for You
If you have encountered information about the rs6170 variant, it is important to approach it with a clear understanding of its limitations. Genetic testing results, especially for rare variants, should never be used to self-diagnose or make medical decisions. The presence of a variant does not guarantee that an individual will experience reproductive health issues, nor does its absence guarantee fertility. If you are concerned about reproductive health or fertility, the most appropriate step is to consult with a reproductive endocrinologist, urologist, or a certified genetic counselor. These professionals can interpret genetic findings within the context of your overall health, medical history, and clinical testing. They can provide personalized guidance and discuss whether further diagnostic testing is appropriate for your specific situation.
How common is this variant?
The rs6170 variant is considered rare, with a low minor allele frequency observed across most studied populations.
Frequently asked questions
Is rs6170 a cause of male infertility?
Research has identified rs6170 in men with spermatogenic impairment, but it is not considered a definitive cause of infertility. Genetic factors are complex, and many variables contribute to reproductive health.
Should I get tested for the FSHB rs6170 variant?
Routine testing for this specific variant is not standard clinical practice. You should discuss any concerns about fertility with a healthcare provider who can determine if genetic testing is relevant to your clinical situation.
Can I change my genotype for rs6170?
No, your genotype is determined at conception and cannot be changed. Genetic variants are inherited from your parents and remain constant throughout your life.
Does this variant affect hormone levels?
While some FSHB variants are known to influence FSH levels, the specific impact of rs6170 on hormone levels is still being studied. Clinical interpretation of such variants requires professional medical evaluation.
Sources & further reading
Educational information only, last refreshed 10/29/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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This missense variant in the FSHB gene is associated with spermatogenic impairment and abnormal sperm counts.
Promoter-adjacent variant linked to FSHB expression, influencing basal follicle-stimulating hormone levels, menstrual cycle duration, and twinning propensity.
Pathogenic loss-of-function variant causing isolated follicle-stimulating hormone deficiency leading to hypogonadotropic hypogonadism.
Functional promoter variant in FSHB influencing serum FSH concentrations and reproductive lifespan.
Variant in the promoter region of FSHB associated with circulating follicle-stimulating hormone levels, age at menarche, and reproductive lifespan.
Located in the promoter of FSHB (c.-211G>T), this variant downregulates follicle-stimulating hormone transcription and is strongly associated with male infertility traits (oligozoospermia) and altered female reproductive lifespan.