Clinical Assessment of the Causes of Hypothyroidism - Essay Example

As autoimmune hypothyroidism is the most common primary cause, detecting the presence of thyroid peroxidase antibodies (TPOAb) will confirm the diagnosis. If these antibodies are absent, other causes of hypothyroidism must be clinically evaluated. (Harrison 2005, pp.2108-2109) Even if the unbound T4 levels are normal, but TSH levels are elevated, it reflects mild hypothyroidism and a thyroid peroxidase antibodies test should be performed. In cases where the patient clinically presents with hypothyroidism, but TSH levels are normal, a pituitary or secondary disease can be expected.

For those patients testing for unbound T4 levels becomes necessary, and if low other causes of hypothyroidism such as drug effects, the euthyroid syndrome can be suspected. A further anterior pituitary evaluation workup is required for such patients. (Harrison 2005, pp.2108-2109) 2: Thyroid-stimulating hormone is an important marker for thyroid activity, mainly because of sensitive negative feedback mechanism. Any increase in thyroid hormone concentration will promptly decrease its production. Similarly, an abnormal decrease in the active form of thyroid hormones will raise its level in the blood.

So a single measurement of TSH can give a lot of information about the activity of the thyroid gland. This is the reason it is used as a screening test for most thyroid abnormalities. If normal, a simple TSH measurement can rule out most primary diseases of the thyroid gland with only a few exceptions. In very cases, elevated TSH may not at all be associated with the thyroid gland and, therefore, may be misleading. For example, TSH may be elevated in a rare TSH secreting pituitary tumour as well.

So after the initial screening test, further tests are required for diagnosis. (Harrison 2005, p.2108) Although TSH can point toward some abnormality of the thyroid gland, it cannot determine the exact underlying pathology. Therefore, further unbound or free T3 and T4 levels are measured to confirm the diagnosis of either hyper or hypothyroidism. So hormone levels in conjunction with TSH levels will provide the complete information for the diagnosis of most thyroid abnormalities. (Harrison 2005, p.2108) 3: The lab results are consistent with hypothyroidism.

The patient has elevated TSH levels with decreased levels of unbound T4. Moreover, the clinical findings of weight gain and fatigue are also indicating decreased thyroid hormones. As discussed earlier, autoimmune destruction of thyroid tissue is the most common cause of hypothyroidism. The disease may be associated with a goitre, as in Hashimoto’s thyroiditis, or at a more chronic stage without a goitre, as in the case of atrophic thyroiditis. The most significant finding is the lymphocytic infiltration in the thyroid tissue accompanied by B cells.

The autoimmune destruction is caused primarily by cytotoxic T cells resulting in decreased T4 production and prompt rise of TSH levels. (Harrison 2005, p.2110) The treatment for hypothyroid patients varies depending on the severity of the disease. For patients with complete loss of hypothyroid function, as in the case of clinical hypothyroidism, levothyroxine daily replacement dose of 1.6µg/kg body weight is administered. Adult patients with age less than 60 are started at lower doses with adjustments done later on depending on the clinical and laboratory findings.

Subclinical hypothyroidism is the initial stage of the disease where the rise in TSH level compensates by increasing thyroid production. In those patients, a very low dose of levothyroxine, about 25-50µg/day, is administered. (Harrison 2005, p.2112)