Explore 10,000+ laboratory markers, in plain English.

Protein that stores iron

Blood Health

FGF-23 (Fibroblast Growth Factor 23) What is FGF-23? FGF-23, or fibroblast growth factor 23, is a hormone-like protein that plays a critical role in phosphate and vitamin D metabolism. It is primarily produced by bone cells (osteocytes and osteoblasts) and acts mainly on the kidneys to regulate: Phosphate excretion in urine Vitamin D activation Calcium-phosphate balance FGF-23 is part of a feedback system that helps maintain normal blood phosphate levels. When phosphate levels rise, FGF-23 secretion increases to help eliminate excess phosphate through the urine and reduce vitamin D activation. Why is FGF-23 Measured? Testing FGF-23 levels is especially useful in diagnosing and monitoring disorders involving abnormal phosphate metabolism, bone health, or kidney function. FGF-23 is most commonly used to evaluate: Hypophosphatemia (low phosphate levels) Chronic kidney disease–mineral and bone disorder (CKD-MBD) Hereditary or acquired rickets/osteomalacia Rare phosphate-wasting disorders Tumor-induced osteomalacia (TIO) By measuring FGF-23, healthcare providers can determine whether phosphate loss is due to overproduction of this hormone or other factors. How FGF-23 Works in the Body FGF-23 reduces blood phosphate by: Decreasing phosphate reabsorption in the kidneys — promoting phosphate excretion in urine. Inhibiting 1α-hydroxylase, an enzyme needed to activate vitamin D (which normally helps absorb calcium and phosphate from the gut). Suppressing PTH (parathyroid hormone) under certain conditions. In essence, FGF-23 works as a phosphate-lowering hormone. When levels are too high or too low, the result is disruption of mineral homeostasis, which can negatively affect bone health, kidney function, and cardiovascular risk. What Conditions Are Associated With Abnormal FGF-23 Levels? Elevated FGF-23 Levels High FGF-23 levels are seen in conditions that involve excess phosphate loss, disrupted bone remodeling, or impaired kidney function. Common causes include: Chronic Kidney Disease (CKD) FGF-23 rises early in CKD to compensate for reduced phosphate excretion. Very high FGF-23 is associated with vascular calcification, left ventricular hypertrophy, and poor cardiovascular outcomes. Tumor-Induced Osteomalacia (TIO) Rare tumors (usually benign) produce excess FGF-23, causing bone pain, muscle weakness, and fractures. X-linked Hypophosphatemia (XLH) or Autosomal Dominant Hypophosphatemic Rickets (ADHR) Genetic disorders where FGF-23 is inappropriately elevated, leading to chronic phosphate wasting and defective bone mineralization. Oncogenic or genetic causes of phosphate wasting Low FGF-23 Levels Less commonly, low FGF-23 levels may be associated with: Hyperphosphatemia (high phosphate) due to inadequate renal excretion Familial tumoral calcinosis (a rare condition marked by soft tissue calcifications and hyperphosphatemia) Low phosphate excretion despite high phosphate levels, often due to impaired FGF-23 production or function Symptoms of FGF-23–Related Disorders High or dysregulated FGF-23 levels may contribute to symptoms such as: Bone pain Muscle weakness Fatigue Recurrent fractures Short stature (in genetic conditions) Joint stiffness or deformities (in rickets or osteomalacia) Abnormal lab findings: low phosphate, low/normal vitamin D, high ALP In CKD patients, elevated FGF-23 may correlate with: Anemia Increased cardiovascular risk Poorer outcomes in dialysis patients How Is the FGF-23 Test Performed? Sample type: Blood (usually serum or plasma) Special considerations: Some labs measure intact FGF-23, while others measure C-terminal fragments. Be sure to interpret results in the context of the assay used. FGF-23 levels may fluctuate based on kidney function, iron status, and time of day. Reference Ranges Reference ranges vary depending on the testing method (intact vs. C-terminal assay) and laboratory. Typical intact FGF-23 levels in healthy individuals are approximately: <100 RU/mL (for intact assay) Some labs use pg/mL with normal ranges typically <50 pg/mL Elevated values must always be interpreted alongside: Serum phosphate Vitamin D Parathyroid hormone (PTH) Creatinine/eGFR (to assess kidney function) Alkaline phosphatase (ALP) and bone markers (for bone health) Clinical Applications and Monitoring In CKD Monitoring FGF-23 can help track phosphate retention and mineral-bone disorder progression. It may serve as an early marker of disordered phosphate handling—often rising before phosphate and PTH. In Rare Bone or Tumor Disorders Helps confirm a diagnosis of hereditary hypophosphatemic rickets or tumor-induced osteomalacia Used to guide imaging and treatment decisions In Phosphate Disorders Differentiates between renal phosphate wasting and other causes of hypophosphatemia Helps determine if the body is inappropriately excreting phosphate Summary FGF-23 is a key regulator of phosphate balance and vitamin D metabolism, with rising clinical importance in conditions like chronic kidney disease, osteomalacia, rickets, and rare phosphate-wasting disorders. Abnormal levels may lead to significant complications in bone health, cardiovascular function, and mineral metabolism. Measuring FGF-23 provides valuable insight when investigating unexplained hypophosphatemia, bone pain, or CKD-related mineral disturbances.

helps in the assessment of liver fibrosis

to estimate the degree of liver fibrosis

found in about 4% to 10% of patients with SSc

Fibrinogen is a key marker included in the Inflammation and Oxidation Test panel by Boston Heart Diagnostics, primarily due to its critical role in the body's clotting process and its association with inflammation. Essentially, fibrinogen is a blood plasma protein that's converted into fibrin by the action of the enzyme thrombin during blood clot formation. This process is crucial for stopping bleeding and initiating the healing process following an injury. However, elevated levels of fibrinogen can indicate an increased risk of clot formation within the blood vessels, which is a significant concern because it can lead to blockages, thereby increasing the risk of heart attacks and strokes. Furthermore, high fibrinogen levels are often seen in response to systemic inflammation and can thus serve as a marker of underlying inflammation. This is particularly relevant in cardiovascular diseases, where inflammation plays a pivotal role. Monitoring and managing fibrinogen levels can be an important part of preventive healthcare strategies, aimed at reducing the risk of serious health issues associated with both excessive clot formation and inflammation.

Blood Clotting

Essential for proper blood clot formation

Fibrosis Score is a non-invasive estimate of liver scarring (fibrosis) derived from routine blood tests—typically AST, ALT, platelet count—and sometimes age or body measurements. It helps determine whether liver injury from fatty liver disease (MASLD/NASH), hepatitis B or C, or alcohol use has progressed to advanced fibrosis or cirrhosis. In general, a low score indicates minimal scarring and low risk, while a high score points to significant fibrosis and the need for further evaluation, often via transient elastography (FibroScan®) or specialist assessment. Clinicians use this score to monitor liver health over time, reduce the need for biopsy, and guide treatment and lifestyle changes aimed at halting or reversing damage. If your score falls into the low or minimal range, it suggests little to no fibrosis and likely good liver function—reassuring evidence that advanced damage is not present right now. Even so, keeping your liver healthy matters: prioritize a balanced diet, regular exercise, healthy body weight, limited alcohol, and management of metabolic risks (blood sugar, cholesterol, blood pressure). Your clinician may advise periodic re-checks of liver enzymes and fibrosis markers—typically every 1–3 years—to confirm stability and catch early changes promptly.

Fibrosis Stage (FibroTest® → METAVIR) expresses how much liver scarring you likely have by converting a FibroTest score (f) into METAVIR stages: f ≥ 0.00–0.21 = F0 (no fibrosis); >0.21–0.27 = F0–F1 (no fibrosis); >0.27–0.31 = F1 (minimal fibrosis); >0.31–0.48 = F1–F2 (minimal fibrosis); >0.48–0.58 = F2 (moderate fibrosis); >0.58–0.72 = F3 (advanced fibrosis); >0.72–0.74 = F3–F4 (advanced fibrosis); >0.74–1.00 = F4 (severe fibrosis/cirrhosis). Lower stages (F0–F1) suggest little to no scarring and routine lifestyle-focused care with periodic rechecks; mid stages (F1–F2) indicate rising risk and may warrant confirmatory elastography (e.g., FibroScan®) and more active treatment of the cause (metabolic, viral, alcohol-related); advanced stages (F3–F4) signal substantial scarring, higher complication risk, and the need for specialist management, imaging, and surveillance. Always interpret your number in clinical context and with the reference ranges printed on your report.

Index for Liver Fibrosis

ANTIBODIES ASSOCIATED WITH: This test by itself is not diagnostic for any condition or disease Atherosclerotic Lesions Osteoarthritis BODY TISSUE: Joint

a 5a-reductase inhibitor

bacterial phyla that dominate the entire human digestive tract

bacterial phyla that dominate the entire human digestive tract

The marker "Firmicutes Phylum" refers to a significant group of bacteria commonly found in the human gut. Firmicutes are one of the most abundant types of bacteria in the human digestive tract, playing a crucial role in the body's ability to digest and absorb nutrients. They are also involved in the synthesis of certain vitamins and the regulation of our immune system. A GI panel often measures the levels of Firmicutes to assess the balance of microbial populations in the gut. An imbalance in these bacteria can be linked to various health conditions, including digestive disorders, obesity, and metabolic issues. When analyzing GI panel results, high or low levels of Firmicutes can provide insights into the individual's gut health, pointing towards potential dysbiosis (microbial imbalance) and guiding appropriate dietary or medical interventions to restore balance and support overall health.