The Impact of Stress on Thyroid Function

Thy­roid dys­func­tion is highly preva­lent in the United States, affect­ing 3.7% of Amer­i­cans accord­ing the the 1997–2002 National Health and Nutri­tion Exam­i­na­tion Sur­vey (NHHES). More may actu­ally expe­ri­ence sub­clin­i­cal hypothy­roidism — when the blood val­ues appear “nor­mal” but hypothy­roid symp­toms remain.

One miss­ing link in the thy­roid debate is the impact of stress. Stress affects thy­roid func­tion in a vari­ety of ways, from appro­pri­ate sig­nal­ing and hor­mone bind­ing, to actual T3 con­ver­sion and even­tual detox­i­fi­ca­tion of inac­tive metabolites:

• High cor­ti­sol slows con­ver­sion of inac­tive T4 into active T3 by affect­ing the enzyme responsible.
• Chronic stress sup­presses the pitu­itary gland which is respon­si­ble for releas­ing thy­roid stim­u­lat­ing hor­mone (TSH) which then leads to T4 and T3 release.
• Not all T4 is con­verted to active T3. Some T4 is con­verted to T3 Sul­fate (T3S) and tri­iodothy­roacetic acid (T3AC)which are inac­tive inter­me­di­ates. This isn’t meant to be a chem­istry les­son so it is only impor­tant to under­stand that these T3 mid­dle guys require action by bac­te­ria in the gut to con­vert them into active T3! Stress inter­feres with gas­troin­testi­nal integrity, lead­ing to bac­te­r­ial imbal­ances, that over time can deplete active T3 production!
• High lev­els of cor­ti­sol put stress on the liver’s abil­ity to detox­ify — as cor­ti­sol itself is detox­i­fied by the liver. T4 is also con­verted to an irre­versibly inac­tive form of T3 called “reverse T3” (rT3). rT3 is cleared out by the liver. With chronic lev­els of stress, the body may become inef­fi­cient at clear­ing out inac­tive r T3. This inac­tive form inter­feres with nor­mal T3 activ­ity. This is one rea­son why blood lev­els of T3 and TSH can be nor­mal, yet dys­func­tion could still be present, in part due to stress!

Aca­d­e­mics like to paint “lin­ear” sto­ries of how the body func­tions. But the body works dynam­i­cally. Mol­e­cules morph in and out of active forms. Pro­teins bind to the hor­mones affect­ing their activ­ity. Even the recep­tor sites are highly regulated. It’s a beau­ti­ful sys­tem to think about, yet a frus­trat­ing sys­tem to “treat”.

Stress is just one exam­ple of the phys­i­cal, psy­cho­log­i­cal, and chem­i­cal fac­tors involved in thy­roid health. The body is a series of inter­con­nected webs of activ­ity. This way, the body can pull from mul­ti­ple streams of resources when cer­tain sys­tems become over­loaded. Too much stress, over time, may dete­ri­o­rate some of these streams, lead­ing per­haps to symp­toms of hypothyroidism.

While stress may be an impor­tant miss­ing link to thy­roid dys­func­tion, remem­ber that it’s just one part of a much larger web.

 Dr. Rine­hart is a Board Cer­ti­fied Clin­i­cal Nutri­tion­ist & Chi­ro­prac­tic nutri­tion­ist prac­tic­ing in North­ern New Jer­sey. His evidence-based, holis­tic nutri­tion approach iden­ti­fies the com­mon pat­terns dri­ving chronic dis­ease processes such as Hashimoto’s thy­roidi­tis, Irri­ta­ble Bowel Syn­drome, and Fibromyal­gia. He offers com­pli­men­tary 15 minute phone con­sul­ta­tions to see if his well­ness approach to health­care is right for you.