Thyroid Health and Running Performance
Thyroid dysfunction is very common, especially in women. Did you know that in the US approx. 20 million people have some form of thyroid dysfunction? BUT at least 60% of that number are unaware they have a condition.
Also, women are approx. 5%-10% more likely than men to develop a thyroid condition and it is thought that 1/8 women will develop a thyroid issue in their lifetime.
Per capita, the figures are thought to be similar in the UK.…. those are quite phenomenal figures so, let’s explore:
1. The thyroid gland and its function
2. Thyroid dysfunction and its impact on running performance
3. Some nutrition and lifestyle factors to support thyroid health.
An outline of Thyroid Function:
The thyroid is a butterfly-shaped endocrine gland that sits on the front of the neck just below the Adam’s apple. It is made up of two lobes – which lie on either side of the wind-pipe, joined by a small bridge of thyroid tissue called the isthmus. Each lobe is about the size of a plum cut in half
The thyroid makes two hormones that it secretes into the blood stream, thyroxine (commonly known as T4) and triiodothyronine (known as T3)
The hypothalamus and pituitary gland located in the brain are the master regulators of the whole endocrine system within the body, which controls ALL hormone production
Regarding thyroid hormone production, the hypothalamus sends instructions to the pituitary gland by releasing thyrotropin-releasing hormone (TRH). The pituitary gland in turn sends instructions to the thyroid gland via thyroid stimulating hormone (TSH). The thyroid then produces and releases T3 and T4
This cascade is regulated by a negative feedback loop. What that means is: When circulating levels of thyroid hormone are high, the hypothalamus decreases its production of TRH, which in turn decreases the pituitary production of TSH, and thus inhibits production of T3 and T4.
When circulating levels are low, the opposite effect takes place in which the hypothalamus signals the pituitary to further stimulate thyroid hormone production.
The thyroid normally secretes roughly 20% of the body’s T3, but ALL of the internally produced T4. T4 is converted to the more metabolically active T3 in tissues throughout the body via a series of different enzymes.
Key functions of the Thyroid Gland and its hormones (T4 and T3) associated with running performance:
Thyroid Test Reference ranges:
STANDARD RANGES OF THYROID HORMONES:
TSH: 0.45 – 4.5 µIU/mL
FreeT4: 0.82-1.77 ng/dL
FreeT3: 2.0-4.4 pg/mL
These are the standard ranges utilized by general medical bodies, however as Practitioners working within the Functional Medicine approach to health, we prefer to focus on optimal levels, which are:
FUNCTIONAL THYROID HORMONE RANGES:
TSH: 1.0-2.0 µIU/mL
Reverse T3: 9.2-24.1 ng/dL (rT3 is the inactive form of T3, but it is very rarely tested for by GP or in hospitals, but can help determine how much bioavailable Thyroid hormone is available).
Thyroid antithyroglobulin antibodies (TAA): Less than 20 IU/mL
Thyroid perioxidase antibody (TPO): Less than 35 IU/mL
Basically, this is when the thyroid gland releases an inappropriate level of thyroid hormones; either too much (known as hyperthyroidism) or too little (known as hypothyroidism).
There are many different causes of thyroid dysfunction including:
This will result in over production and secretion of thyroid hormone
Common signs and symptoms for thyroid dysfunction?
Hypersecretion of thyroid hormones:
More severe symptoms include: a rapid heartbeat. Irregular rate and rhythm of heartbeat, fever
Hyposecretion of thyroid hormones:
The impact of thyroid dysfunction on running performance:
If hypothyroidism is the concern, this may impact a runner due to:
If hyperthyroidism is the concern, this may impact a runner due to:
Nutrition interventions to support thyroid health:
To help support hypofunction:
To help support hyperfunction:
With hyperfunctioning of the thyroid gland, generally intervention is necessary
BUT, there are some dietary approaches that could be introduced to help limit the effects of thyroid overstimulation including:
Lifestyle factors to consider for Thyroid support:
The suggestions we make during this episode are for guidance and
advice only, and are not a substitute for medical advice or treatment.
If you have any concerns regarding your health, please contact
your healthcare professional for advice as soon as possible.
Aileen Smith and Karen Campbell met at as nutrition students (Institute for Optimum Nutrition, London) and became lifelong friends and nutritional buddies! Both have a love of running and a passion for nutrition, delicious food and healthy living.
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