ComorbidityHypothyroidism has been frequently associated with other diseases. These co-morbid states include infertility, menstrual irregularities, Type 1 diabetes mellitus, depression, obesity, hypercholesterolaemia, etc.
- Hypercholesterolaemia
Impaired thyroid function may be the cause of a hypercholesterolaemia. Clinical studies have shown that hypothyroid patients have significantly elevated serum cholesterol levels - from about 30% to 50% above control values. Also increase in low density lipoprotein (LDL) cholesterol, modest fasting hypertriglycereidaemia has been observed in hypothyroid patients, particularly when they are obese.
- Diabetes Mellitus
Approximately 10% of patients with Type 1 diabetes mellitus develop chronic thyroiditis in their lifetime which may include the insidious onset of subclinical hypothyroidism. Insulin requirements may change in the presence of subclinical hypothyroidism. It is important to examine patients with diabetes for the development of a goitre.
- Infertility
Some patients with infertility and menstrual irregularities have underlying subclinical or clinical hypothyroidism. In some patients with elevated TSH levels, thyroxine replacement therapy may normalize the menstrual cycle and restore normal fertility.
- Depression
The diagnosis of subclinical or clinical hypothyroidism must be considered in suspected patients with depression. In fact, a small proportion of all patients who are depressed have primary hypothyroidism - either overt or subclinical. Also all patients on lithium therapy need periodic thyroid evaluation because lithium may induce goitre and hypothyroidism.
- Obesity
Some obese patients may have hypothyroidism. Caloric needs due to hypothyroidism may be responsible for weight gain in these persons.
In view of the strong association between hypothyroidism and the above comorbid states, it is advisable to look for hypothyroidism in these patients and screen accordingly through T4 and TSH testing.
Diagnosis
I Clinical Criteria
- History taking to evaluate patients at risk
- Symptoms/signs of thyroid hormone deficiency
- Evidence of disease/previous treatment or exposure known to cause thyroid/pituitary/ hypothalamic failure
- Conditions associated with increased risk of chronic autoimmune thyroiditis
II Laboratory Testing
Specific tests
Include measurement of TSH, T4 or FT4 (Free T4), T3 or, FT4 (Free T3)
In primary hypothyroidism
Decreased T3, T4 levels with elevated TSH or Normal T3 low T4 and high TSH / Low T3 occurs in severe cases
In subclinical hypothyroidism
Normal T3, T4 levels with elevated TSH levels
In central hypothyroidism
Low T3, and T4 levels with normal or low T3, T4, TSH Levels |
