Mr Khalid Ahmed MB BS MRCP(UK) FRCP is an endocrinologist at Bupa Cromwell Hospital and West Middlesex Hospital.
Thyroid disorders are some of the most prevalent medical problems affecting up to one percent of the general population. The female-to-male ratio is up to 20-to-1 making it a predominantly, although not exclusively, a female disorder. Thyroid disease can have a significant effect on a woman’s health including menstrual disturbances and fertility problems.
There two active thyroid hormones - Tetraiodothyronine (T4) and Triiodothyroinine (T3). T4 is produced exclusively by the thyroid gland, while T3 is produced in small amounts by the thyroid gland but is mostly produced peripherally by deiodination of T4. T3 is the more effective hormone, with up to 20 times the efficacy of T4.
Thyroid hormones exert their effects by binding to nuclear receptors in virtually every cell in the body. They control energy production, hence the widespread effects in body systems seen with thyroid dysfunction.
Primary thyroid failure is the most prevalent thyroid problem in the general population.Hashimoto’s thyroiditis is the most common cause. Other causes include post-partum thyroiditis and iatrogenic thyroid failure (thyroidectomises or radio-iodine therapy).
Its incidence is around 6 new cases per 1,000 of the population annually and affects up to two percent of the female population.
Presenting symptoms include:
- weight gain
- dry skin
- hair loss
- general muscle aches
- disturbed menstrual cycle (menorraghia or oligomenorrhea)
- Elevated thyroid stimulating hormone (TSH)
- Low normal or low free T4
- Positive thyroid peroxisomal antibodies (anti-TPO antibodies)
Treatment of hypothyroidism
Levothyroxine (T4) is the standard treatment. It is usually started at a low dose and titrated upwards to achieve biochemical euthyroid state and symptom relief. The use of combined T4/T3 is not recommended as an initial approach. A minority of patients may benefit from this combination, but it should be used with great caution in view of the high risk of toxicity.
Pitfalls in the diagnosis of hypothyroidism
The ‘sick euthyroid state’ is a reflection of the body’s own adaptive mechanisms to combat acute illness. It is mainly reflected in the thyroid stimulating hormone (TSH) levels. TSH is low during acute illness and will rise above the upper limit of normal during the recovery phase. It can take up to 12 weeks to reach equilibrium. Therefore, a diagnosis of hypothyroidism should be made with great caution during acute illness and the recovery period after acute illness.
This is an autoimmune mediated destructive thyroiditis occurring in the weeks and months after delivery. It can occur up to nine months after delivery with a median of 13 weeks. Its incidence has been reported to be five to nine percent of unselected post-partum women.
It starts with an initial biochemical and clinical thyrotoxic phase due to overspill of thyroid gland stores as a result of the inflammatory state. This is followed by a hypothyroid phase with ultimate complete recovery in the majority of patients.
It is vital to recognise this condition as the management is different from other causes of thyroid dysfunction.
During the toxic phase, beta-blockers, if not contraindicated, could be used to control symptoms of thyroxin excess. Anti-thyroid drugs are not indicated as the condition is that of a destructive thyroiditis, not of overproduction.
In the hypothyroid phase, the management is dictated by the severity of symptoms. In some patients one might be able to monitor without thyroid hormone treatment. In others, the severity of symptoms dictates treatment with thyroxin for up to 12 months. At that stage one can consider withdrawal of treatment for up to eight weeks and observing for potential recovery of the thyroid gland.
These patients should have thyroid function tests at annual intervals if fully recovered. In the presence of positive anti-TPO antibodies, up to 50 percent are likely become permanently hypothyroid within seven years.
We should be aware that Graves’ thyrotoxicosis can present de novo in the post-partum period, necessitating careful evaluation of these patients prior to diagnosis and treatment.