Anorexia nervosa, a serious eating disorder, involves extreme food restriction and maintaining a low body weight. Individuals with anorexia often have a distorted body image, perceiving themselves as overweight even when they are significantly underweight. This disorder can lead to various physical complications due to chronic malnutrition.
Hypothyroidism is a condition where the thyroid gland does not produce enough thyroid hormones. These hormones are crucial for regulating the body’s metabolism and energy use, affecting nearly every organ. When thyroid hormone levels are insufficient, various bodily functions can slow down.
How Anorexia Affects Thyroid Function
Anorexia nervosa significantly impacts the body’s endocrine system, particularly the hypothalamic-pituitary-thyroid (HPT) axis, which regulates thyroid hormone production. Severe calorie restriction and low body weight, characteristic of anorexia, induce a physiological adaptation aimed at conserving energy. This adaptive response is often referred to as “euthyroid sick syndrome” or “non-thyroidal illness syndrome” (NTIS).
In NTIS, the body reduces the conversion of thyroxine (T4), a less active thyroid hormone, into triiodothyronine (T3), the more active form. This process results in lower levels of T3, while T4 levels may remain normal or be slightly low. Thyroid-stimulating hormone (TSH), produced by the pituitary gland to signal the thyroid, can be normal or even slightly suppressed in this state, rather than elevated as typically seen in primary hypothyroidism. This altered hormone profile is the body’s way of slowing down metabolism to cope with energy deprivation, making it a protective mechanism rather than a primary thyroid gland failure.
This differs from true primary hypothyroidism, where the thyroid gland itself is dysfunctional and fails to produce enough hormones, leading to consistently high TSH levels as the pituitary tries to stimulate the failing gland. In anorexia, the thyroid gland is generally healthy, but its function is altered due to the extreme nutritional stress.
Identifying Thyroid-Related Symptoms
Individuals with low thyroid hormone levels, whether due to true hypothyroidism or the functional changes seen in anorexia, can experience a range of symptoms. Common signs include fatigue, feeling cold more than usual, constipation, dry skin, and hair thinning or loss. Other symptoms can include a slowed heart rate (bradycardia), muscle aches, and difficulty concentrating or “brain fog”.
Many of these symptoms also commonly occur in individuals with anorexia nervosa due to the direct effects of malnutrition and low body weight. The body’s attempt to conserve energy in starvation leads to a reduced metabolic rate, which can manifest as these overlapping symptoms. This overlap makes it challenging to determine whether symptoms are solely due to the eating disorder, an altered thyroid state, or a combination of both without a thorough medical evaluation.
Addressing Thyroid Issues and Recovery
Assessing thyroid function in individuals with anorexia typically involves blood tests that measure TSH, T3, and T4 levels. These tests help differentiate between a true primary thyroid disorder and the adaptive changes of non-thyroidal illness syndrome (NTIS). In cases of NTIS, the primary approach is nutritional rehabilitation and weight restoration, rather than thyroid hormone replacement therapy.
As an individual’s nutritional status improves and weight is gained, thyroid hormone levels, particularly T3, often normalize without the need for specific thyroid medication. Thyroid hormone replacement is generally avoided in NTIS because it can increase metabolic rate, potentially hindering weight gain, and may negatively impact bone mineral density, which is often already compromised in individuals with anorexia. Professional medical and nutritional guidance is important to ensure a safe and effective recovery process, as full normalization of thyroid function can take weeks to months. If initial test results do not resolve with nutritional improvement, further evaluation may be needed to rule out underlying primary hypothyroidism.