A 56-year-old woman is evaluated for persistent fatigue. A year ago, she developed panhypopituitarism following resection of a large nonfunctional pituitary tumor. Current treatment includes hydrocortisone and levothyroxine, with her most recent dose adjustment a few months ago. The patient has had no associated headaches, excessive urination, visual disturbances, or weight change. Vital signs are normal. BMI is 26 kg/m² with no change in weight over the last 6 months. Physical examination is unremarkable.
Laboratory results are as follows:
An MRI of the pituitary 6 months ago showed no residual pituitary tumor. Which of the following is the most appropriate next step in management of this patient's disorder?

Question

A 56-year-old woman is evaluated for persistent fatigue. A year ago, she developed panhypopituitarism following resection of a large nonfunctional pituitary tumor. Current treatment includes hydrocortisone and levothyroxine, with her most recent dose adjustment a few months ago. The patient has had no associated headaches, excessive urination, visual disturbances, or weight change. Vital signs are normal. BMI is 26 kg/m² with no change in weight over the last 6 months. Physical examination is unremarkable.
Laboratory results are as follows:

An MRI of the pituitary 6 months ago showed no residual pituitary tumor. Which of the following is the most appropriate next step in management of this patient's disorder?

Quizplus · Accepted Answer

11ec193a_97d1_5aa8_853d_df6aa3538384_MD0002_00 Pituitary tumors are the most common cause of central (secondary) hypothyroidism, which can arise due to compressive effects of the tumor or as a complication of surgery or radiation therapy. The diagnosis is established by a low serum free T4 associated with a low (or inappropriately normal) TSH. This patient has central hypothyroidism and is on levothyroxine therapy but her persistent fatigue suggests possible under-replacement. Unlike primary hypothyroidism, TSH in central hypothyroidism demonstrates minimal response to levothyroxine supplementation. Nearly all patients with central hypothyroidism on thyroid replacement therapy have undetectable TSH; and patients whose levothyroxine dose is inadequate (eg, due to decreased absorption or increased metabolic demands) most often do not exhibit a rise in TSH. Therefore, levothyroxine dosing in central hypothyroidism should be based on serum free T4 levels, with the dose adjusted to maintain T4 in the high-normal range. (Choices A and D) T3 is produced primarily by deiodination of T4 in peripheral tissues. Serum T3 levels (total and free) correlate poorly with overall thyroid physiologic status and are less reliable than T4, although they are occasionally used in the evaluation of hyperthyroidism in patients with normal T4 levels, in those with alterations in thyroid-binding proteins, or in those with euthyroid sick syndrome. T3 has a shorter half-life than T4, and liothyronine (T3) therapy can lead to fluctuations in physiologic status and increased risk of thyrotoxicosis. Studies have not shown superiority of combined replacement over levothyroxine (T4) alone. (Choice C) Disruption of other pituitary hormones is common in central hypothyroidism. However, insulin-like growth factor 1 levels (eg, as used in the assessment of growth hormone deficiency) can be low in a hypothyroid state, and adequate levothyroxine dosing should be confirmed before measuring insulin-like growth factor 1. (Choice E) A low (ie, suppressed) TSH in primary hypothyroidism indicates over-replacement and warrants a dose reduction. However, this relationship does not hold in central hypothyroidism. Educational objective: Levothyroxine therapy in central hypothyroidism should be based on serum free T4 levels, with the dose adjusted to maintain T4 in the high-normal range. TSH in central hypothyroidism demonstrates minimal responsiveness to levothyroxine and may not rise in patients with inadequate replacement. __________ References: Clinical review: central hypothyroidism: pathogenic, diagnostic, and therapeutic challenges. (http://www.ncbi.nlm.nih.gov/pubmed/22851492)

A 56-Year-Old Woman Is Evaluated for Persistent Fatigue