I very much appreciated Dr Douglas Ross's article, Subclinical Hypothyroidism: When to Treat, When to Watch (CONSULTANT, September 1, 2006, page 1121), and I have several questions for him.
Are menstrual irregularities associated with subclinical hypothyroidism?
When you treat subclinical hypothyroidism, what should be the starting dosage of levothyroxine?
Once treatment has been initiated, how do you determine whether the dosage needs to be reduced or increased? Do you rely solely on the thyroid-stimulating hormone (TSH) level, or do you also take the patient's symptoms into account?
- Suzanne Barron, MS, RN, CS Rocky Mount, Va
Thank you for your interest in my article. Here are my responses to your questions:
Subclinical hypothyroidism is unlikely to cause menstrual irregularities.
Initial treatment of hypothyroidism, either subclinical or overt, depends on the patient. For a healthy patient, I prescribe a little less than the expected full replacement dosage, eg, 100 µg/d for a typical middle-aged woman. For elderly patients or those with underlying heart disease, a lower initial dosage followed by gradual increases is advisable. Note that because of negative feedback to pituitary production of TSH, a dose that is less than a person's normal hormone production rate will not make him or her hyperthyroid, even if he is only slightly hypothyroid before treatment.
With regard to monitoring therapy, I rely on TSH levels. Hypothyroid symptoms are notoriously unreliable indicators.
- Douglas S. Ross, MD Associate Professor of Medicine Harvard Medical School Boston