Last Updated on April 26, 2026
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If you have or at some point have suspected that you had hypothyroidism, you might have noticed that most discussions about hypothyroidism commonly highlight symptoms such as fatigue, weight gain, cold intolerance, and dry skin. However, lesser-known yet significant changes may occur in your sensory experiences, particularly changes in taste and smell.
Before we talk about how hypothyroidism can affect a person’s senses of smell and taste, let’s take a cursory look at what the terms “thyroid” and “hypothyroidism” mean. The thyroid gland is a butterfly-shaped gland located in the neck and produces thyroid hormones, primarily T3 (triiodothyronine) and T4 (thyroxine). Hypothyroidism means your thyroid gland is underactive and not producing enough of these hormones. These hormones regulate your metabolism, energy production, and the health of many organs, including your brain and sensory systems. Primary causes of hypothyroidism include autoimmune diseases like Hashimoto’s thyroiditis, certain medications, radiation therapy, and iodine deficiency. According to the American Thyroid Association, hypothyroidism affects about 5% of the U.S. population based on older population-based studies, with women and older adults being particularly at risk.
Unfortunately, low levels of thyroid hormones can slow down nerve conduction, impair the transmission of sensory signals to the brain, and reduce brain responsiveness. Cranial nerves such as the olfactory nerve (for smell or olfaction) and the facial, glossopharyngeal, and vagus nerves (for taste or gustation) can be indirectly affected by low levels of these hormones. This impairment could explain the sensory anomalies noted in hypothyroid individuals, explained in more detail in this blog article.
In this article, we will answer the following questions:
Is there significant scientific evidence linking hypothyroidism to these sensory changes?
Yes, there is generally enough scientific evidence that hypothyroidism can indeed affect the senses, particularly of sense and taste.
According to a recently published narrative review on this topic in the journal Cureus Journal of Medical Science, research into how hypothyroidism affects the senses began as early as 1975. One study published in the American Journal of Medicine found that nearly 40% of the participants with untreated hypothyroidism reported a reduced sense of smell. Results from quite a number of studies have shown that hypothyroid patients generally show improvements in olfactory function upon receiving thyroid hormone replacement therapy, indicating some connection between thyroid hormone levels and olfactory function.
As far as changes in taste are concerned, they are surprisingly common in hypothyroidism, with about half of patients experiencing foods that taste more bitter or metallic. A study published in 2016 in Experimental and Clinical Endocrinology & Diabetes comparing untreated hypothyroid patients to healthy individuals found that sweet and bitter tastes were especially dulled. Fortunately, after three to six months of thyroid hormone treatment, participants showed significant improvements across all four basic tastes (sour, sweet, salty, and bitter).
One other study published in 2016 in PLOS ONE found that even people with subclinical hypothyroidism can experience a reduced sense of smell and difficulty tasting bitterness. The good news is that with proper treatment (with levothyroxine), these issues often improve within about three months. Interestingly, research has also shown that even after treatment with levothyroxine, about 5% of patients continued to experience problems with taste. This suggests that while thyroid hormone therapy can improve sensory issues for many, some changes in smell and taste may persist even after treatment.
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Download ThyForLife for FreeWhat are the mechanisms behind altered smell and taste in hypothyroidism?
The physiological mechanisms behind sensory alterations in hypothyroidism involve multiple pathways.
To begin with, did you know that your body constantly regenerates taste buds and olfactory receptor cells? How cool is that! Unfortunately, hypothyroidism slows down the metabolic processes underlying the maintenance and regeneration of the sensory receptor cells in the nose and tongue, leading to weaker senses. Interestingly, a scientific study published in Biomed Research International in 2016 looked at how hypothyroidism (low thyroid hormone levels) affects the sense of smell. Researchers tested how quickly the brain responded when participants smelled odors like mint and anise. They found that people with clear symptoms of hypothyroidism had noticeably slower brain responses to smells compared to healthy people and those with mild (subclinical) hypothyroidism. This means that low levels of thyroid hormones can slow down how smell signals travel to and are processed by the brain.
Second, hypothyroidism can lead to decreased blood flow and, as a result, poor tissue oxygenation. This lack of oxygen and nutrients impairs the functionality of the olfactory epithelium (the tissue in the nose responsible for detecting odors) and taste buds. Additionally, research indicates that the olfactory bulb (the brain region involved in processing smells) may shrink in hypothyroid conditions, affecting the brain’s ability to accurately process scent signals. A recent study published in European Archives of Oto-Rhino-Laryngology found that people with Hashimoto’s thyroiditis often have smaller olfactory bulbs, the part of the brain that processes smells. Interestingly, this shrinkage was only seen in those with low thyroid levels, not in patients whose thyroid function remained normal.
Finally, the inflammation associated with autoimmune thyroid disorders like Hashimoto’s thyroiditis may contribute to damage in sensory pathways, worsening the loss of smell and taste, especially when combined with thyroid hormone deficiency.
What are some common changes in smell and taste reported in hypothyroid individuals?
Some hypothyroid patients report a partial loss of smell, making it difficult to detect subtle odors like perfumes, flowers, or cooking scents. Some individuals also experience an altered taste sensation, where familiar foods taste unusually bland, overly salty, metallic, or just “off”. In severe or untreated cases, a complete loss of smell can occur, deeply impacting appetite and quality of life.
These changes can be gradual or sudden and often lead to decreased enjoyment of food, loss of appetite, and unintended weight changes. Some individuals might even develop safety concerns, such as an inability to detect smoke or spoiled food.
Here’s a brief list of a list of the names of some signs and symptoms to watch for and what they mean:
- Hyposmia (Reduced sense of smell)
- Hypogeusia (Diminished sense of taste)
- Anosmia (Complete loss of smell)
- Ageusia (Complete loss of taste)
- Parosmia (Distorted smell perception)
- Dysgeusia (Distorted taste perception)
Of course, these symptoms could also arise from other causes (see the FAQs below), so it’s important not to jump to conclusions without consulting your healthcare provider.
FAQs
In some cases, sensory changes may persist even after thyroid hormone levels have normalized. Possible reasons include irreversible damage to the olfactory or gustatory pathways, delayed neuronal regeneration, or concurrent conditions such as chronic sinusitis or autoimmune inflammation.
If your senses remain altered even after your thyroid levels are normalized, it’s wise to consult an ENT (ear, nose, and throat specialist) or a neurologist to rule out other causes. A thorough re-evaluation is needed to rule out other underlying issues. Advanced therapies such as olfactory training programs, which involve repeated exposure to specific scents, can help improve residual dysfunction over time.
If you’re experiencing unexplained sensory changes, you definitely should consult your healthcare provider. Diagnosing sensory changes in hypothyroidism requires a thorough clinical evaluation. To this end, healthcare providers often start with a detailed medical history and physical examination, focusing on the onset, duration, and characteristics of the sensory alterations.
Typically, doctors may recommend:
- Thyroid function tests to assess levels of thyroid stimulating hormone (TSH), T3, and T4.
- ENT examinations to rule out structural causes such as nasal polyps or infections.
Yes, typically by comparing with aging, neurological disorders, and infections. Sensory changes are not unique to hypothyroidism. Aging, neurodegenerative diseases (like Parkinson’s or Alzheimer’s), and respiratory infections such as COVID-19 can also cause smell and taste dysfunction. A comprehensive clinical evaluation is essential to pinpoint the exact cause.
Choosing foods with strong, contrasting flavors (like citrus, herbs, or spices) can enhance eating pleasure despite reduced sensory perception.
Additionally, olfactory training (a therapy involving daily exposure to different scents) has shown promise in enhancing smell recovery for individuals with various causes of sensory loss.
Key takeaways
- Despite their significant impact on daily life, changes in smell and taste are often overshadowed by more prominent symptoms of hypothyroidism. Many patients and even healthcare providers may not immediately associate these sensory changes with thyroid dysfunction.
- A deficiency in thyroid hormones can lead to slowed nerve conduction, reduced cellular metabolism, and impaired sensory receptor function. The result of this is the disruption of sensory processes such as smell and taste.
- Over time, these sensory alterations can lead to decreased appetite, unintentional weight loss or gain, and even emotional disturbances due to diminished food enjoyment.
