Hypothyroidism is a disorder in which the thyroid gland produces too little of the hormones triiodothyronine (T3) and thyroxine (T4). Symptoms that may indicate problems with the secretion of thyroid hormones include, m.in constant feeling of cold, drowsiness, weight gain, constipation or problems with getting pregnant. What causes hypothyroidism and can it be cured for the condition?