A 63-year-old man comes to the office due to fatigue, lethargy, constipation, dry skin, loss of libido, and cold intolerance for the past 4 months. He has been previously healthy except for a stage I nasopharyngeal tumor treated with radiation 10 years ago. He currently takes no medications. The patient has a 20-pack-year smoking history but quit after being diagnosed with cancer. There is no history of alcohol or illicit drug use.
Blood pressure is 100/70 mm Hg and pulse is 60/min. Examination shows dry skin with normal pigmentation. Visual fields are normal on confrontation. The oropharynx is normal. Testes are normal in size but soft. Deep-tendon reflex relaxation time is prolonged.
Laboratory results received at 8:00 AM are as follows:

An MRI of the pituitary reveals no mass lesions.
Which of the following is the most appropriate next step in management of this patient?

Question

A 63-year-old man comes to the office due to fatigue, lethargy, constipation, dry skin, loss of libido, and cold intolerance for the past 4 months.  He has been previously healthy except for a stage I nasopharyngeal tumor treated with radiation 10 years ago.  He currently takes no medications.  The patient has a 20-pack-year smoking history but quit after being diagnosed with cancer.  There is no history of alcohol or illicit drug use.
Blood pressure is 100/70 mm Hg and pulse is 60/min.  Examination shows dry skin with normal pigmentation.  Visual fields are normal on confrontation.  The oropharynx is normal.  Testes are normal in size but soft.  Deep-tendon reflex relaxation time is prolonged.
Laboratory results received at 8:00 AM are as follows:

An MRI of the pituitary reveals no mass lesions.
Which of the following is the most appropriate next step in management of this patient?

Quizplus · Accepted Answer

11ec193a_97c6_d343_853d_e721d30bdcaf_MD0002_00 This patient's symptoms (fatigue, constipation, dry skin, loss of libido, cold intolerance) and low-normal TSH/low free T₄ suggest central hypothyroidism. Central hypothyroidism is much less common than primary hypothyroidism and is usually due to the destruction of pituitary thyrotrophs by mass lesions, intracranial radiation therapy, or infiltrative disorders of the pituitary/hypothalamus (eg, hemochromatosis, sarcoidosis). Due to the risk of pituitary mass lesions, patients with central hypothyroidism should undergo imaging with MRI (preferred) or CT. ₄ Central hypothyroidism has a similar (though often milder) presentation to primary hypothyroidism. However, symptoms can vary with coexisting pituitary abnormalities, which are commonly present. Initiating treatment for hypothyroidism prior to diagnosing and treating concurrent adrenal insufficiency may induce adrenal crisis (Choice D). Although this patient's morning cortisol level is within the normal range, low-normal cortisol levels may be seen frequently in adrenal insufficiency. A cosyntropin stimulation test is recommended. (Choice A) A 24-hour urinary cortisol excretion is used for evaluation of suspected Cushing's syndrome. Low urinary cortisol excretion may be seen in adrenal insufficiency, but this test is neither sensitive nor specific for this condition. (Choice C) Total testosterone (free plus protein bound) is usually an accurate reflection of total body testosterone secretion. Free testosterone levels are assessed if there are suspected abnormalities in testosterone binding to sex hormone-binding globulin. (Choice E) Thyroid peroxidase antibody titers are typically elevated in autoimmune (Hashimoto's) thyroiditis. These patients usually present with primary hypothyroidism (low free T₄, elevated TSH), or occasionally, with a transient hyperthyroid phase (elevated free T₄, suppressed TSH). ₄ ₄ Educational objective: Central hypothyroidism can be due to mass lesions, intracranial radiation therapy, or infiltrative disorders of the pituitary/hypothalamus. It often coexists with other pituitary deficiencies. Initiating treatment of hypothyroidism prior to diagnosing and treating coexisting adrenal insufficiency may induce adrenal crisis. __________ References: Radiation-induced hypopituitarism: a review (http://www.ncbi.nlm.nih.gov/pubmed/22594901)

A 63-Year-Old Man Comes to the Office Due to Fatigue