In areas without iodine deficiency the common causes of chronic hypothyroidism are autoimmune thyroid disease, thyroidectomy, radiotherapy (both radioiodine therapy and external beam radiotherapy congenital disorders and disorders of thyroid hormone metabolism.Most papillary thyroid cancer patients will undergo a total thyroidectomy. With the total removal of the thyroid gland, your body can no longer naturally produce thyroid hormones. Thyroid hormones are essential because they control your body's metabolism.
Subjects were free of thyroid cancer and had no evidence of any residual thyroid function. These patients were compared to a group of 3875 patients with normal thyroid function despite benign thyroid nodules less than 2 cm in size.Levothyroxine monotherapy cannot guarantee euthyroidism in all athyreotic patients. PLoS One 2011:6:e22552. Epub August 1, 2011. SUMMARY OF THE STUDY This was a study of 1811 patients (1530 women and 281 men) who became hypothyroid following a total thyroidectomy for thyroid cancer and were receiving hormone replacement with T4 alone.
BACKGROUND Thyroxine (T4) is the main hormone secreted by the thyroid gland. It is converted to the active hormone T3 in other cells in the body, most commonly in the liver, kidney and in the cells where thyroid hormone works.A morning cortisol less than 100 nmol/L always indicates the need for ongoing steroid replacement. Results greater than 500 nmol/L indicate adequate reserve and values in between may require provocation tests.
If the patient discovers they have missed one (or more) doses they can take the missed doses in conjunction with their usual dose over the next few days. The absorption of thyroxine may be reduced by cholestyramine, colestipol, aluminium hydroxide, ferrous sulfate and possibly fibre.Variable daily dosing removes the need for patients to cut thyroxine tablets. Problems If taken correctly, thyroxine should enable patients to lead a normal life. However, there are some common problems which can affect management.
Secondary hypothyroidism occurs with some pituitary and hypothalamic diseases. Diagnosis. Patients may not present with the typical clinical features of hypothyroidism. They may have vague symptoms such as tiredness. The diagnosis can be made by finding a persistently elevated serum concentration of thyroid stimulating hormone (TSH).DESIGN : Prospective study. All patients were initiated on 100 g levothyroxine and titrated to within the reference range for TSH and free T4. Correlations to height, weight, age, lean body mass (LBM body surface area (BSA) and body mass index (BMI) were calculated.
Thyroxine dose Thyroxine has a half-life of 7-10 days but a much longer biological effect. Once-daily dosing is appropriate. The dose is dependent on body weight and age. Children require larger doses of thyroxine per kg body weight than adults who require approximately 1.6 microgram/kg/day.RESULTS : Correlations were seen between levothyroxine dose and patient age (r-0.346, P 0.01 bodyweight (r0.296, P 0.01 LBM (r0.312, P 0.01 BSA (r0.319, P 0.01) and BMI (r0.172, P 0.05).
For example, 100 microgram/day (700 microgram/week) may be inadequate to control the TSH but 125 microgram/day (875 microgram/week) may be too much. A dose of 800 microgram/week can be taken as 100 microgram/day five days a week and 150 microgram/day two days a week.Moreover, there was a wide range of variability in the T3/T4 ratios in T4-treated patients suggesting a wide range in peripheral T3 levels in different individuals. In fact, more than 20 of the T4-treated patients did not maintain FT3 and FT4 levels in normal range despite normal TSH levels.
Concerns regarding the bioavailability of different preparations are not relevant in Australia. Thyroxine tablets should be kept dry and cool and in their original container. 3 Recent advice to refrigerate thyroxine tablets increases the likelihood of moisture causing deterioration in the medication.The use of lithium and iodine-containing preparations (such as amiodarone) can cause a drug-induced hypothyroidism. Providing patients with a copy of the laboratory results which confirm their need for thyroxine often proves helpful for the patient and future treating doctors.
Monitoring and dose adjustment In primary hypothyroidism the TSH alone can be used to monitor therapy. The aim should be to maintain the TSH at the lower end of the normal range ( mIU/L).Both T4 and T3 are important in maintaining normal metabolic function. In individuals with normal thyroid function, 10-15 of the daily T3 production comes from the thyroid gland. In patients who have no functioning thyroid (ie are hypothyroid the absence of T3 production by the thyroid can be overcome by maintaining higher circulating T4 levels.
Replacement therapy means the goal is a TSH in the normal range and is the usual therapy. Suppressive therapy means that the goal is a TSH below the normal range and is used in thyroid cancer patients to prevent growth of any remaining cancer cells.At the start of treatment a patient does not need measurement of their TSH until they have been on their predicted dose of thyroxine for 4-6 weeks (unless symptoms of thyrotoxicosis dictate otherwise).
INTRODUCTION AND AIM: New entities, such as 'subclinical' over- and undersubstitution, are easily diagnosed after thyroid surgery due to improved testing methods, and the incidence of thyroidectomy with lifelong hormone substitution is increasing.Worsening symptoms of coronary disease or heart failure should be controlled before increasing the dose of thyroxine and a dose reduction may be necessary while cardiac disease is stabilised. For patients between these two extremes, a starting dose of 50 microgram/day is reasonable.
5 Drug-induced hypothyroidism Lithium and iodine are the common causes of drug-induced hypothyroidism. Amiodarone, iodine-containing contrast media and kelp tablets are common sources of large doses of iodine. All forms of drug-induced hypothyroidism will usually resolve on withdrawal of the drug.Animal thyroid medications are made from dried out pig thyroid glands. Some patients prefer these natural alternatives to their synthetic counterparts because they assume these drugs are the safest treatment. However, many doctors believe that synthetic thyroid hormones are the bestand safestoption.
There is no proven benefit in adding liothyronine to the treatment of patients who have persistent symptoms despite taking thyroxine. Secondary hypothyroidism If there is pituitary or hypothalamic disease, TSH is unreliable for diagnosing and monitoring thyroid function and fT4 should be used instead.It is helpful to consider if the patient's symptoms are likely to be due to hypothyroidism before prescribing thyroxine and to tell them if you suspect that some of their symptoms are unlikely to respond.
It is extremely important to consider cortisol deficiency before starting treatment with thyroxine in patients with pituitary and hypothalamic disease as its use will speed the metabolism of cortisol and can induce an adrenal crisis.The present study identifies a subgroup of hypothyroid patients, namely those whose thyroid was surgically removed who do not have normal FT4 and FT3 levels despite normal TSH levels on T4 alone.
WHAT ARE THE IMPLICATIONS OF THIS STUDY? Hypothyroid patients are typically treated with T4 alone. A number of studies have demonstrated that T4 alone is sufficient for the majority of hypothyroid patients.Thyroid surgery is the first-line of treatment for papillary thyroid cancer (also known as papillary thyroid carcinoma). In most cases, you will need to take thyroid hormone replacement therapy to manage hypothyroidism after surgery.
When the thyroxine dose is in the range of 100-200 microgram/day, variable daily dosing may be necessary to achieve euthyroidism. Considering the total weekly dose is helpful when changing the dose.2 Most adults will maintain euthyroidism with a dose of thyroxine of 100-200 microgram/day. There may be a decline in thyroxine requirements in the elderly. Both brands of thyroxine currently available in Australia come from the same supplier and are identical.
Lifelong thyroxine therapy relieves symptoms and restores 'normal' thyroid function. Commencing thyroxine can aggravate cardiac disease but is relatively free of adverse effects. The concentration of thyroid stimulating hormone is used to monitor therapy.OBJECTIVE : Optimal thyroxine replacement following total thyroidectomy is critical to avoid symptoms of hypothyroidism. The aim of this study was to determine the best formula to determine the initiated replacement dose of levothyroxine immediately following total thyroidectomy.