Thyroid functioning is evaluated by tests of hormonal parameters: TSH, fT4 and fT3.
In particular, TSH values allow to trace the patient’s condition. When TSH range is between 0.4 and 4.0 mUI/L we talk about euthyroidism, that is to say normal functioning of the thyroid gland. It is associated with fT4 and fT3 normal values.
If TSH range is over 4.0 mUI/L or below 0.4 mUI/L there is an alteration of the thyroid functioning: respectively hypothyroidism and hyperthyroidism.
Hyper and hypothyroidism can be either subclinical or overt, according to the thyroid hormones levels.


Subclinical hypothyroidism

It is characterised by a greater level of TSH (TSH > 4.0 mUI/L)and normal levels of fT4 and fT3. It implies the beginning of an insufficient thyroid activity.
The symptoms are the same as overt hypothyroidism though more blurred. In particular: sleepiness, weight gain, problems with memory, cold intolerance. Moreover, subclinical hypothyroidism is associated with metabolic syndrome, as well as an increase in cholesterol and in cardiovascular risk. The main problem of subclinical hypothyroidism is its turning into overt hypothyroidism. It is often associated with autoimmune thyroiditis, therefore with an inflammatory state. Regular check are fundamental to slow down the development of overt hypothyroidism.


Overt hypothyroidism

In overt hypothyroidism, TSH levels are high and T4 and T3 levels are low. Since the thyroid hormones are important to several metabolic processes, their decrease turns into a general ill feeling. The symptoms are the same as subclinical hypothyroidism but more serious.


Subclinical hyperthyroidism

TSH value is below the threshold of normality (TSH < 0.4 mUI/L) and is accompanied with normal fT4 and fT3 values. It is difficult to diagnose it, also due to the similarity of its symptoms with different pathologies. For example, blurred palpitations, arrhythmia, tachycardia can occur and be misinterpreted as direct cardiovascular diseases. Another alarm bell is the patient’s bone metabolism that gets altered when there is an excessive production of thyroid hormones and consequently a higher risk of fractures and osteoporosis.


Overt hyperthyroidism

We talk about overt hyperthyroidism when TSH levels are extremely low and T4 and T3 levels are above average. Hyperthyroidism is often associated with nodular goiter. A common hyperthyroidism symptom associated with Graves’ disease is swollen eyes. The symptoms are definitively serious and mostly concern heart and bones. Hyperthyroidism can also be associated with altered metabolism of fats, sugars and proteins.