Anti-Thyroglobulin Antibodies

Thyroid marker

TgAb

Anti-Thyroglobulin Antibodies

Category: Thyroid
Unit: IU/mL

Autoantibodies against thyroglobulin, a protein produced by the thyroid gland. Elevated levels indicate autoimmune thyroid disease, most commonly Hashimoto's thyroiditis. Also used in thyroid cancer monitoring, where TgAb interferes with thyroglobulin tumour marker assays.

PED Notes

AAS are broadly immunosuppressive and may suppress autoantibody production, so TgAb may appear deceptively low on-cycle. Check during off-cycle or cruise periods for a more accurate reading. GH increases T4-to-T3 conversion and may unmask latent autoimmune thyroiditis in susceptible individuals. Exogenous T3 (Cytomel) profoundly suppresses TSH, which can mask a developing autoimmune process. After T3 discontinuation, TSH rebound can amplify the autoimmune response and temporarily spike TgAb.

When elevated (>4 IU/mL):

Diagnostic workup:

  • Full thyroid panel: TSH, Free T4, Free T3, TPO Antibodies
  • Thyroid ultrasound if TgAb >20 IU/mL or if TPO Antibodies are also elevated
  • If on exogenous T3: taper off and recheck full thyroid panel (including TgAb and TPOAb) 6-8 weeks after discontinuation
  • Repeat TgAb in 3-6 months to assess trend; a rising titre is more clinically significant than a single elevated value

Supplements (evidence-based):

  • Selenium (Selenomethionine) -- 200mcg/day: Supports thyroid antioxidant defence. Do NOT exceed 400mcg/day
  • Myo-Inositol -- 600mg/day (with selenium 83mcg): Shown to reduce both TPOAb and TgAb by up to 51% in autoimmune thyroiditis
  • Vitamin D3 -- 5000 IU/day if deficient (<75 nmol/L): Deficiency is strongly associated with autoimmune thyroid disease. Aim for 75-150 nmol/L
  • Zinc (Picolinate) -- 30mg/day: Cofactor for thyroid hormone synthesis and immune regulation
  • Omega-3 (EPA/DHA) -- 2-3g/day: Anti-inflammatory; may help modulate the autoimmune response

Lifestyle:

  • Consider gluten assessment; autoimmune thyroiditis has a documented association with coeliac disease
  • Ensure adequate iodine intake (150-300mcg/day) but do NOT mega-dose (excess iodine worsens autoimmune thyroiditis)
  • Reduce chronic stress; elevated cortisol disrupts thyroid axis regulation

PED-specific:

  • If on exogenous T3 (Cytomel): elevated TgAb suggests underlying autoimmune thyroiditis. Taper T3 gradually (reduce by 12.5mcg every 5-7 days) and investigate thyroid health independently
  • If on AAS: androgens are immunosuppressive, so TgAb may appear deceptively low on-cycle. Check during off-cycle or cruise periods
  • If on GH: GH increases T4-to-T3 conversion and may unmask latent thyroid autoimmunity. Monitor every 3-6 months while on GH
  • Post-contest prep: severe caloric restriction alters immune function. Recheck 8-12 weeks after returning to maintenance calories

When low / undetectable (<1.8 IU/mL):

  • Normal finding. No intervention required.
  • Indicates no significant autoimmune attack on thyroglobulin

References:

  • Caturegli, P., De Remigis, A., & Rose, N. R. (2014). Hashimoto thyroiditis: Clinical and diagnostic criteria. Autoimmunity Reviews, 13(4-5), 391-397. DOI: 10.1016/j.autrev.2014.01.007
  • Feldt-Rasmussen, U., & Rasmussen, A. K. (2023). Thyroglobulin and thyroglobulin antibody: An updated clinical and laboratory expert consensus. European Journal of Endocrinology, 189(2), R11-R25. DOI: 10.1093/ejendo/lvad100
  • Fröhlich, E., & Wahl, R. (2017). Thyroid autoimmunity: Role of anti-thyroid antibodies in thyroid and extra-thyroidal diseases. Frontiers in Immunology, 8, 521. DOI: 10.3389/fimmu.2017.00521

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Frequently Asked Questions

Reference Ranges

Standard Range

0 - 4 IU/mL

VitalMetrics Range

0 - 2 IU/mL

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