Description

Thyroid Health and Running Performance

Introduction

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.  

Show Notes

(09:09)

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. 

(12:50)

Key functions of the Thyroid Gland and its hormones (T4 and T3) associated with running performance:

1. Metabolic rate - Most of us will be aware of their importance in maintaining metabolic rate. T4 and T3 control metabolism (i.e. the way the body uses energy) by regulating the speed with which the body cells work. So, we could think of our bodies as being a car, and the thyroid hormones as the engine. Increased metabolic rate =  increase body heat production
2. Energy expenditure - by regulating the rate at which energy is burned. This can therefore affect weight loss or weight gain.
3. Cardiac function – Thyroid hormones can slow down or speed up the heartbeat, they are also known to increase heart muscle contractibility and cardiac output. They are also known to promote vasodilation (widening of blood vessels), which leads to enhanced blood flow to many organs.
4. Fat metabolism – thyroid hormones enhance utilisation of fatty acids in many tissues and are linked to plasma concentrations of cholesterol and triglycerides. E.g. when thyroid hormones are low, there is an increase in blood cholesterol concentration, in fact increased cholesterol levels is one diagnostic feature of hypothyroidism. 
5. Carbohydrate metabolism: Thyroid hormones stimulate almost...