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What does it mean to have an underactive thyroid?

You can think of the thyroid as the central gear in a sophisticated engine. If that gear breaks, the entire engine goes down with it.



The thyroid gland is a butterfly shaped endocrine organ located in the frontal part of your neck. The hormones produced by the thyroid are responsible for the most basic aspects of body function, impacting all major systems within your body. You can think of the thyroid as the central gear in a sophisticated engine. If that gear breaks, the entire engine goes down with it.

What does it mean to have hypothyroidism (underactive thyroid)

When the thyroid is not functioning optimally, a cascade of hormonal events takes place affecting several glands and hormones of the endocrine system and all the physiological processes they regulate. The end result is one of two main types of thyroid conditions: hyperthyroidism or hypothyroidism.

In this article we’ll explore all aspects of hypothyroidism and discuss why the functional medicine approach has a much more comprehensive toolkit to diagnose and treat this hugely complex disease.

What Is Hypothyroidism?

According to the National Institute of Health (NIH) Hypothyroidism, also called underactive thyroid, is when the thyroid gland doesn’t make enough thyroid hormones to meet your body’s needs [1]. The prevalence of underactive thyroid is 2% in the UK and seems to be more common in women [2]. However, this doesn’t tell the whole story as thyroid disease often goes undiagnosed.

Symptoms of underactive thyroid

  • Weight gain
  • Constipation
  • Mental fogginess and poor memory
  • Fatigue
  • Poor circulation and numbness in the hands and feet
  • Thinning hair or hair loss
  • Puffy and sensitive face
  • Depression
  • High cholesterol
  • Oedema
  • Poor vision
  • Feeling cold
  • Chronic digestive problems
  • Dry/brittle hair and skin
  • Morning headaches
  • Muscle stiffness, aches and tenderness
  • Infertility and changes in menstrual cycle
  • Hoarseness
  • Decreased sweating


The two major causes of hypothyroidism are:

1. Nutrient deficiency

  • Iodine. Thyroid hormone is rich in iodine, and deficiency of iodine can lead to hypothyroidism.
  • Zinc is required for the synthesis of thyroid hormone, and deficiency of zinc has been shown to result in hypothyroidism.
  • Selenium, is required to convert T4 (inactive thyroid hormone) into T3 (active form of thyroid hormone).

2. Hashimoto’s disease

In Hashimoto’s disease, the body attacks the thyroid gland, progressively destroying its capacity to produce thyroid hormone and resulting in hypothyroidism.


The reason isn’t clear, but sometimes, inflammation of the thyroid occurs after pregnancy. This is called postpartum thyroiditis. Women with this condition usually have a severe increase in thyroid hormone levels followed by a sharp drop in thyroid hormone production. Most women with postpartum thyroiditis will regain their normal thyroid function but some may end up developing hypothyroidism.

Diagnosis of Hypothyroidism

There is an ongoing debate about the diagnosis of hypothyroidism. The standard blood test available on the NHS currently looks at one, possibly two thyroid markers. One is TSH and the other one is T4. Testing for such a limited number of markers often leads to under-diagnosis or misdiagnosis and the patient often walks away thinking their thyroid function is fine. Find out more about our comprehensive thyroid tests here.

Look at your hands

Weak and brittle nails with ragged cuticles are common physical signs of hypothyroidism. If you have these symptoms and also suffer with fatigue, hair loss (especially a thinning of the lateral eyebrows), low libido, dry skin, and unexplainable weight gain, it is possible that you have hypothyroidism.

Risk factors

The thyroid is the ‘sentinel’ for the environment. The function of the thyroid gland is designed to be induced or suppressed in response to changes in the environment. As the environment changes, the function of the thyroid gland will change.

From the functional medicine perspective, we consider 8 environmental domains as key risk factors in the development of hypothyroidism:

  • Infections: Viral infections such as Epstein-barr can be a potential trigger for poor thyroid health, so an important consideration whilst investigating thyroid health.
  • We often investigate if toxins, particularly heavy metals, play a part as they seem to be key triggers in the development in hypothyroidism [3].
  • Adrenal stress is probably the most common problem we encounter in functional medicine and the thyroid is no exception. Adrenal stress can manifest in many ways, leading to autoimmunity, thyroid resistance, reduced conversion of T4 (non-active) to T3 (active) and disruption to the endocrine system [4].
  • Antigens/Gut function: Poor gut health can suppress thyroid function and trigger Hashimoto’s disease, and low thyroid function can lead to an inflamed and leaky gut. It’s important to mention gluten sensitivity and celiac here, as research shows a strong link between hypothyroidism and gluten intolerance [5] [6].
  • Nutrition: For a healthy thyroid, the most crucial nutrients include Iodine, Selenium, Zinc, and vitamin A, B, C, and tyrosine [7] [8]. Deficiencies of these nutrients can lead to the development of hypothyroidism.
  • Medication: Thyroid physiology is very vulnerable to negative influences from many commonly prescribed and widely used medications.
  • Movement, sleep and relationships are also huge part of the functioning of the body and we cannot ignore the power of these lifestyle factors when investigating and treating hypothyroidism.


In the current conventional system, when a patient is diagnosed with hypothyroidism they are often prescribed levothyroxine to counteract the symptoms of low thyroid hormone, regardless of the cause. But is it likely that that patient will go on to develop other health conditions because the underlying cause has not been addressed? Patients with underactive thyroid function have a much higher prevalence of obesity, diabetes, osteoarthrosis, osteoporosis, asthma, hypertension, dyslipidemia, infertility, mental health issues; low thyroid function is a symptom among a collection of other related symptoms with an underlying and unifying connection [9] [10] [11]. The role of functional medicine is to investigate and address that connection, while the medication manages the symptoms.

Hypothyroidism Treatment

When we are confronted with sub-optimal or blatant thyroid dysfunction in our clinic, we must always ask two questions:

  1. What is happening upstream that is disrupting thyroid function?
  2. What else is going wrong in the body as a result of poor thyroid function?

Simply identifying poor thyroid health and giving the same old nutrients, herbs or hormones to ‘support’ the thyroid gland itself is inadequate in both approach and understanding. At the London Clinic of Nutrition, we take a functional medicine approach to assessing your thyroid health. Our approach is always personalised and keeps the patient’s specific needs and lifestyle in mind.


After a thorough assessment into your health and lifestyle, our dietary program focused on improving thyroid function would include the following:

  • High in pre and probiotic foods to address dysbiosis [12]
  • High in phytonutrients; think about eating for a rainbow.
  • Low in the Omega-6 and high on Omega-3 [13]
  • Low in saturated and trans fats
  • Eating organic produce as much as possible to reduce toxin exposure is always recommended.

Foods to avoid

At our clinic, we often find that eliminating some of the potentially problematic foods may be necessary.

  • Patients with hypothyroidism often find a significant improvement in their symptoms by fully eliminating gluten from their diet.
  • Goitrogens and soya may also be problematic for individuals with low thyroid function.

Can you still lose weight if you have underactive thyroid?

In short, possibly. But as hypothyroidism is so multifactorial and is caused by a myriad of environmental factors (and also causes systemic complications) it totally depends on the individual.

Read more about thyroid treatment here.


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