A 36-year-old woman comes to the office for follow-up of hypothyroidism. She has no current symptoms. The patient was diagnosed with hypothyroidism secondary to Hashimoto's thyroiditis 4 years ago. She takes 150 µg levothyroxine daily before breakfast and her dose has been stable for the last year. Physical examination, including thyroid examination, is normal.
Thyroid function tests are as follows:

Which of the following is the best next step in management of this patient?

Question

A 36-year-old woman comes to the office for follow-up of hypothyroidism.  She has no current symptoms.  The patient was diagnosed with hypothyroidism secondary to Hashimoto's thyroiditis 4 years ago.  She takes 150 µg levothyroxine daily before breakfast and her dose has been stable for the last year.  Physical examination, including thyroid examination, is normal.
Thyroid function tests are as follows:

Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

11ec193a_97cd_14dd_853d_3d7c830e844e_MD0002_00 Synthetic levothyroxine (LT₄) is the preferred replacement therapy for hypothyroidism. Most actions of the thyroid hormone in the body are mediated through triiodothyronine (T₃), which is secreted in active form by the thyroid gland (15%-20%) and also converted from thyroxine (T₄) in extrathyroidal tissues (80%-85%). Because a large percentage of T₃ is formed from T₄ conversion in the peripheral tissues, patients with hypothyroidism are usually able to achieve adequate T₃ levels with LT₄ treatment alone. ₄ ₃ ₄ ₃ ₄ ₃ ₄ The recommended therapeutic goal in patients with primary hypothyroidism is to maintain TSH within the normal reference range. Serum TSH is the most reliable marker of levothyroxine replacement therapy in hypothyroid patients as it reflects the biologic activity of thyroid hormones in the tissues (ie, hypothalamus). For this reason, TSH alone is usually sufficient to monitor LT₄ treatment in patients with primary hypothyroidism. However, despite this recommendation, thyroid hormone levels are frequently ordered by practitioners along with TSH to monitor LT₄ therapy. ₄ ₄ (Choices A and D) In most patients on LT₄ therapy who have a TSH within the reference range, circulating T₃ levels will also be within the reference range. In some cases, treatment with LT₄ alone may fail to restore plasma T₃ to a level within the reference range despite a normal TSH. However, the significance of this low T₃ is unknown, and the American Thyroid Association recommends against increasing the LT₄ dose, treating with combination LT₄ and liothyronine (T₃), or switching to liothyronine alone in these patients. ₄ ₃ ₄ ₃ ₃ ₄ ₄ ₃ (Choice C) Levels of free T₄ above the reference range are often observed during replacement therapy with LT₄, especially if the blood sample is drawn 1-3 hours after LT₄ administration. This condition is not associated with adverse events, and the dose of LT₄ should not be changed. ₄ ₄ ₄ ₄ (Choice E) Thyroid peroxidase (TPO) antibodies are useful for diagnosis in cases of subclinical hypothyroidism, recurrent miscarriages, and euthyroid diffuse goiters. However, there is no benefit to measuring TPO antibodies once the diagnosis of Hashimoto's thyroiditis has been established (as in this patient). Educational objective: The therapeutic goal in primary hypothyroidism is to maintain TSH levels within the normal reference range by replacement with levothyroxine. Levothyroxine dose adjustment should be based on TSH levels alone rather than direct measurement of thyroid hormone levels. __________ References: Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. (http://www.ncbi.nlm.nih.gov/pubmed/23246686)

A 36-Year-Old Woman Comes to the Office for Follow-Up of Hypothyroidism