Did You Know About the Thymus?

By Adrienne Stewart, ND

The Endocrine system is clearly the foundational topic of EndoANP.  We commonly discuss thyroid, pituitary, and ovarian function.  However, we often don’t discuss the thymus gland.  For this month’s newsletter, I want to highlight the THYMUS:

Did You Know?  

  • The thymus weighs 12-15 grams at birth, reaches its maximum weight of about 40 grams (about 1 ounce) around puberty, and then shrinks and persists in an atrophic state into old age.
  • Thymosin is the hormone of the thymus, and it stimulates the development and production of T-lymphocytes.
  • The thymus is most active during the neonatal and pre-adolescent periods and is later replaced by adipose tissue.  The atrophy (involution) is due to the increasing circulating level of sex hormones.
  • When the thymus gland is active, it helps the body protect itself against autoimmunity through the process of central tolerance and therefore, plays a vital role in the immune and endocrine systems.
  • The thymus is made up of a cortex and medulla where thymocytes undergo a process of selection.  First, T cells undergo functional “Positive Selection” in the cortex and then undergo autoreactive “Negative Selection” in the medulla.  Negative Selection is where T cells with high affinity interaction are eliminated through apoptosis to avoid autoimmunity.  Cells that pass both levels of selection are then released into the bloodstream.
  • DiGeorge syndrome is a genetic disorder that leads to a congenital defect in thymus development.  Patients may present with a profound T cell deficiency and therefore immunodeficiency.
  • Patients with myasthenia gravis commonly have thymic hyperplasia or malignancy and a thymectomy may be recommended for patients with myasthenia gravis.
  • And lastly, in some cultures, animal thymic tissue is used for consumption as a type of sweetbread.  Thymus, anyone?

After learning a little more about the thymus, I have to wonder the extent of impact on thymus function and autoimmunity when xenoestrogens and other Endocrine Disrupting Compounds are introduced at an early age.  Could this cause an early involution and therefore compromised immunity?  Likely so.


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