MODERN CONCEPTS OF PRIMARY THYROID-GLAND FAILURE

Primary thyroid gland failure is a common medical disorder occurring i n mild or severe forms in 10% to 15% of our population. Symptoms may b e classical and easy to recognize or very subtle, escaping clinical de tection. This disorder is more common in females and increases with ad vancing age. The most important diagnostic test is measurement of the serum thyrotropin (TSH) concentration, which will increase above the n ormal range in both mild and severe cases. Most clinical effects of th yroid hormone deficiency can be explained by the ''nuclear thyroid hor mone hypothesis,'' which states that thyroid hormones act predominantl y by effecting the transcription of key genes in affected tissues. The rapy of hypothyroidism is easy, inexpensive, and precise, involving pu re L-thyroxine and measuring dose requirements and efficacy by monitor ing serum TSH concentrations.