What is Hypothyroidism?
The thyroid gland is a butterfly shaped gland situated just below your Adam’s apple in the neck. The thyroid gland is part of the endocrine system and produces two hormones; thyroxine (T4) and triiodothyronine (T3) with T3 being the more potent and T4 being converted to T3 in the body. These two hormones are important in metabolism and the metabolic rate. Excess thyroid hormone results in a high metabolic rate increased heartrate and weight loss whereas deficient thyroid hormone results in a low metabolic rate, low body temperature, slow pulse and weight gain.
What causes Hypothyroidism?
Hypothyroidism occurs when the thyroid gland fails to secrete enough thyroid hormones. Hypothyroidism can be a result of dysfunction of the thyroid gland (primary hypothyroidism) or less commonly a result of failure of the pituitary (secondary hypopituitarism), which stimulates the thyroid through the hormone TSH (Thyroid Stimulating Hormone). The most common cause of primary hypothyroidism is autoimmune destruction of the thyroid gland. This is where the body’s own immune system attacks the thyroid gland and prevents it producing thyroid hormone. Less commonly the thyroid maybe removed surgically because of thyroid lumps or tumours resulting in long term hypothyroidism. Secondary hypothyroidism during pituitary disease is most commonly caused by a benign pituitary tumour or surgery for the tumour. Rarely, hypothyroidism can be congenital (inherited) and this can be both primary and secondary.
How common is Hypothyroidism?
Hypothyroidism is the most common thyroid disorder; prevalence rises with age and affects about 3% of the general population. Diurnal estimates that there are over 2 million patients suffering from hypothyroidism in Europe alone and over 32 million worldwide.
What are the symptoms of Hypothyroidism?
The signs and symptoms of hypothyroidism are relatively nonspecific but include: tiredness, weight gain, cold intolerance, constipation, joint and muscle pain, dry skin, thin and brittle hair or fingernails. In younger patients it may be a cause of infertility or poor growth.
What is the current treatment?
The majority of patients are currently treated with thyroxine (T4) tablets. These are taken on a daily basis. However, some patients may take T3 with T4 or T3 alone.
What are the limitations of current treatment for Hypothyroidism?
Current standard of care is T4 monotherapy; however, up to 20% of patients treated with T4 monotherapy have unsatisfactory health outcomes with increased weight, lipid levels, depression and a poor quality of life. There is a body of evidence, suggesting these poor health outcomes are because T4 monotherapy does not replace the physiological level of T3 in the body. T3 has a short half-life in the circulation and current formulations of T3 give unphysiological peaks and troughs: there is no T3 formulation that can replace physiological T3 levels. European guidelineshighlight the high unmet patient need in this area and that there is an urgent requirement for further research and development of combination therapies of T4 and T3.