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Hypothyroidism

A 57 years old Malay man presented with complaint of numbness of hands and feet for 2 weeks. It was associated with tiredness and cold intolerant as well. A blood test was done on him, and it revealed following: TSH > 100.0, FT4: 1.8 pmol/L (12-22), FT3: 0.9 pmol/L (3.1-6.8). In addition it also showed total cholesterol of 10.56, TG 3.26, HDL 1.58, LDL 7.5 mmol/L.

A diagnosis of primary hypothyroidism was made and he was started on thyroid supplement. On 13 March 2015, he came back for a follow up. He felt much better but still having tiredness and cold intolerant. A follow up blood test was done again and it showed an improvement of TFT as follows; TSH: 18.34, FT4: 16.5 pmol/L, FT3: 4.2 pmol/L. His thyroid supplements were fine tuned.

Discussion:

Hypothyroidism is a clinical entity commonly seen by the primary care physician. Untreated hypothyroidism can contribute to hypertension, dyslipidemia, infertility, cognitive impairment, depression, myxedema coma and neuromuscular dysfunction. Hypothyroidism is also a common underlying factor in children who are frequently sick such as allergies and viral infections.  The prevalence increases with age. Hypothyroidism may be a result of primary gland failure or insufficient thyroid gland stimulation by the hypothalamus or pituitary gland.  Clinical presentations of hypothyroidism are nonspecific and may be subtle, especially in older persons. These include weight gain, fatigue, poor concentration, depression, diffuse muscle pain, and menstrual irregularities. Symptoms with high specificity for hypothyroidism include constipation, cold intolerance, dry skin, proximal muscle weakness, and hair thinning or loss.

The leading laboratory appraisal of thyroid function is a serum thyroid-stimulating hormone test. Apparent primary hypothyroidism is diagnosed with an elevated serum TSH level and a low serum free T4 level. An increased serum TSH level with a normal range serum free T4 level is consistent with subclinical hypothyroidism. A low serum free T4 level with a low, or inappropriately normal, serum TSH level is consistent with secondary hypothyroidism and will usually be associated with further evidence of hypothalamic-pituitary insufficiency.Family physicians will most commonly encounter patients with primary hypothyroidism as secondary hypothyroidism is present in only 5 percent of cases. In most of the patients, alleviation of symptoms can be achieved through oral administration of levothyroxine, and most patients will require lifelong therapy. In older patients and in patients with heart disease, the initial dosage of levothyroxine is generally 25 mcg or 50 mcg daily, with the dosage increased by 25 mcg every three to four weeks until the estimated full replacement dose is reached. Thyroid hormone increases heart rate and contractility, and therefore increases myocardial oxygen demand.

Consequently, starting at higher doses may precipitate acute coronary syndrome or an arrhythmia.  The overwhelming evidence available in the literature supports the notion that L-T4 monotherapy provides adequate thyroid hormone replacement in patients with hypothyroidism. However, a small subset of hypothyroid patients does seem to have a better quality of life and perform better on cognitive tests when placed on combination T4/T3

therapy. According to one large study, this could be explained by the Thr92Ala polymorphism in the DIO2 gene, which is present in about 15% of the general population. While a prospective trial studying the effect of the Thr92Ala polymorphism on the neuropsychiatric response to combined T3/T4 versus L-T4 monotherapy has yet to be carried out, it is fascinating to contemplate the notion that personalized medicine is rapidly catching up with modern thyroidology.

T4 needs to be converted to its active form T3. Mineral deficiency such as Selenium deficiency and Vitamin deficiency such as B vitamin deficiency makes this conversion difficult for most of us making COMPOUNDED T3 and T4 together as a better choice.  Most hypothyroid patients are left untreated as Drs only accept the diagnosis when the levels of T4 and T3 are below the reference range. However the level for optimum health should be in the 25 th  centile ( about 75 % of the upper limit ) .

Prepared by Dr Lee Cheng Yew.

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