Hypothyroidism and iron deficiency are two of the most common conditions that affect women’s health today. Have you been treated for hypothyroidism but still can’t get your TSH and Thyroid hormone levels to budge? Or have you been prescribed thyroxine medication and no matter how high your doctor increases your dose your hair is still thinning, and you still feel zapped of energy? Well, iron deficiency could be the missing link in your treatment back to wellness. Both hypothyroidism and iron deficiency share some similar symptoms that include:

• Fatigue
• Hair loss
• Dry skin
• Sensitivity to the cold
• Reduced peripheral circulation
• Brain fog
• Heavy or irregular periods
• Muscle weakness

It’s not as simple as stating “I’m fatigued because I have hypothyroidism” or “I’m just tired because I’m iron deficient”. More often than not, these two conditions are not isolated and are in actual fact co-morbidities. Let’s have a look at the pathological dance between these two conditions.

How does hypothyroidism affect iron levels?

1. Iron homeostasis is dependent on Iron Regulating Proteins (IRPs) and the Iron Responsive Element (IRE) activity. Active thyroid hormone T3 has been found to modulate hepatic ferritin expression by acting on the IRP and IRE pathway. Reduced T3 levels in hypothyroidism down-regulates IRP and therefore down-regulates the production of ferritin by the liver [1]. Several studies have found that serum ferritin levels are reduced in hypothyroid patients and elevated in hyperthyroid patients [2][3][4].
2. Hypothyroidism can reduce hydrochloric acid production and impair iron absorption [5][6].
3. Thyroid hormones stimulate erythropoiesis- the production of red blood cells. Reduced circulating thyroid hormones T4 and T3 results in reduced red blood cell levels contributing to anaemia [7].

How does iron deficiency contribute to hypothyroidism?

1. The thyroid peroxidase enzyme (TPO) is responsible for the first two steps in thyroid hormone synthesis. TPO is a heme-containing enzyme and therefore its activity is dependent on iron. In iron deficiency, there is reduced TPO activity and therefore reduced thyroid hormone production [8].
2. Some studies have suggested that the reduced oxygen carrying capacity in iron deficiency inhibits the peripheral conversion of T4 to the active T3 thyroid hormone [9][10].
3. Iron deficiency appears to reduce the binding of T3 hormone to its Thyroid Binding Receptor sites (TRs) and therefore reduces T3 activity [8].

So, what came first the chicken- hypothyroidism or the egg- iron deficiency? I think it is clear by now that both conditions can trigger the onset of the other. The real take-away message is the importance of investigating and treating both conditions simultaneously. If you only treat the thyroid, you may find some symptoms linger and will make you think your treatment isn’t working- look at your iron levels. If you find you cannot live without ongoing iron supplementation or your ferritin stores don’t seem to budge with supplementation- look to your thyroid. Trying to accelerate an engine when the handbrake is on simply won’t work. Working with a naturopath can help you identify what your handbrakes are and come up with a targeted treatment plan that can accelerate you back to wellness.