Aishling Hannigan-Murphy

Aishling Hannigan-Murphy

Aishling Hannigan-Murphy

Hypothyroidism or an “underactive thyroid” is a condition where the thyroid gland produces inadequate thyroid hormones (1). Common symptoms include, weight gain, fatigue, cold intolerance, hair loss, constipation and poor memory (2). It is estimated that 2% of the UK population have hypothyroidism, in which 5% are over 60 years. “Women are 5 to 10 times more likely to be affected than men” (1).

The complex relationship between our “stress hormone” cortisol and the thyroid gland which influences thyroid function and production is well acknowledged in functional therapeutic practices. Let’s delve further into this topic.

What is the thyroid gland?

The thyroid gland is a butterfly shaped organ located in the base of the front of the neck (3). Follicular cells of the thyroid produce two thyroid hormones of approximately 80% thyroxine (T4) and 20% triiodothyronine (T3) (2). Mostly inactive T4 is converted to active T3 in tissues of the liver, kidneys, skeletal muscle and brain. T3 carries out the majority of thyroid function. This process is governed by the hypothalamus-pituitary-thyroid axis (2).

The thyroid regulates the body’s metabolism by increasing or decreasing the metabolism of carbohydrates, fats and proteins. Nearly every cell has receptors for thyroid hormones, which means these hormones can have an effect on most organ systems in the body (2).

What happens in times of stress?

Our stress response, “Fight or Flight”, is activated by a perceived threat or physical, emotional, psychological or physiological stress when ill, via the sympathetic nervous system (4). Brief acute stressors may be beneficial in terms of enhancing the immune system, cognitive function and improving performance (5).

However, chronic sustained stressors can lead to constant activation of our stress response triggering hypothalamic-pituitary-adrenal (HPA) axis over stimulation (6). The hypothalamus is located in the brain above the pituitary gland, while the adrenal glands sit on top of the kidneys. Prolonged HPA axis activation can put pressure on these hormonal signalling pathways, leading to the eventual dysregulation of the axis and excessive cortisol output (6). This can persist for years affecting many body systems including altered thyroid function (4,6).

How does chronic cortisol production affect thyroid function?

  1. Blunts the secretion of thyroid stimulating hormone (TSH) released by the pituitary gland in the brain, a key regulator of thyroid hormone production (4,7). If inflammation is present due to constant activation of the stress response, inflammatory cytokines (messengers) may further supress TSH secretion (4).
  2. Inhibits thyroid hormone conversion of less active T4 to active T3 (4). A person may show normal blood T4 levels but may be functionally deficient in T3.
  3. Increases conversion of T4 thyroid hormone to inactive reverse T3 hormone, at the expense of active T3 thyroid hormone. This may slow down metabolism, lowering calorie needs to support survival (7,8).

What can help to restore homeostasis to the HPA axis?

  • Manage stress. Try relaxation practices to help the body build resilience to stress, such as yoga, meditation, deep belly breathing, gratitude and self -compassion.
  • Improve quality of sleep.
  • Undertake gentle exercise. High intensity exercise can lead to chronic raised cortisol levels (9).
  • Reduce any inflammatory agents that may raise cortisol levels such as food sensitivities, autoimmune diseases, obesity and xenobiotics (environmental toxins).
  • Balance blood sugar.
  • Reduce stimulants such as coffee and nicotine, which activate the stress response (10, 11).
  • Support the adrenal glands with foods containing vitamins B1, B2, B3, B5, B6, vitamin C and magnesium.

In summary, the adrenal glands release cortisol in response to stress, although it is important that levels return to normal following a stressful event. If this doesn’t happen it may lead to HPA axis dysregulation, causing high cortisol output. This may affect thyroid health, mental well-being and quality of life.

Aishling Hannigan-Murphy is a qualified nutritional therapist and is continuing her studies in Personalised Nutrition.


  1. National Institute for Health Care Excellence (NICE). Context: Thyroid disease: Assessment and management: Guidance [Internet]. 2023 [cited 2023 Oct 19]. Available from:
  2. Shahid MA, Ashraf MA, Sharma S. Physiology, thyroid hormone - StatPearls - NCBI Bookshelf [Internet]. 2023 [cited 2023 Oct 25]. Available from:
  3. National Health Service (NHS). Overview -Underactive thyroid (hypothyroidism) Contents [Internet]. NHS; 2021 [cited 2023 Oct 19]. Available from:
  4. Tsigos C, Kyrou I, Kassi E, Chrousos GP. Stress: Endocrine physiology and pathophysiology - endotext - NCBI [Internet]. 2020 [cited 2023 Oct 22]. Available from:
  5. Dhabhar FS. The short-term stress response – mother nature’s mechanism for enhancing protection and performance under conditions of threat, challenge, and opportunity. Frontiers in Neuroendocrinology [Internet]. 2018 [cited 2023 Oct 25];49:175–92. Available from:
  6. Karin O, Raz M, Tendler A, Bar A, Korem Kohanim Y, Milo T, et al. A new model for the HPA axis explains dysregulation of stress hormones on the timescale of weeks. Molecular Systems Biology [Internet]. 2020 [cited 2023 Oct 25];16(7). Available from:
  7. Yaamarthy V, Rani CJ, Hemamalini R, Ahmed MI. Evaluation of serum cortisol levels in patients with hypothyroidism at a tertiary care hospital, Telangana, India: A case-control study. JOURNAL OF CLINICAL AND DIAGNOSTIC RESEARCH [Internet]. 2023 [cited 2023 Oct 23]; Available from:
  8. Malik R, Hodgson H. The relationship between the thyroid gland and the liver. QJM [Internet]. 2002 [cited 2023 Oct 23];95(9):559–69. Available from:
  9. Hill EE, Zack E, Battaglini C, Viru M, Viru A, Hackney AC. Exercise and circulating cortisol levels: The intensity threshold effect. Journal of Endocrinological Investigation [Internet]. 2008 [cited 2023 Oct 24];31(7):587–91. Available from:
  10. Corti R, Binggeli C, Sudano I, Spieker L, Hänseler E, Ruschitzka F, et al. Coffee acutely increases sympathetic nerve activity and blood pressure independently of caffeine content. Circulation [Internet]. 2002 [cited 2023 Oct 24];106(23):2935–40. Available from:
  11. Manta E, Konstantinidis D, Dimitriadis K, Tatakis F, Drogkaris S, Polyzos D, et al. Correlations between sympathetic nervous system activity and smoking, as well as unattended blood pressure in essential hypertension. European Heart Journal [Internet]. 2021 [cited 2023 Oct 24];42(Supplement_1). Available from:
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