A 45-year-old man comes to the clinic reporting a 5-month history of worsening fatigue, ge… — USMLE Step 2 CK

A $45$ -year-old man comes to the clinic reporting a $5$ -month history of worsening fatigue, generalized weakness, decreased libido, and cold intolerance. He has also experienced an unintentional weight loss of $5 \text{ kg}$ ( $11 \text{ lb}$ ) and frequent morning headaches. Vital signs show a blood pressure of $96/58 \text{ mm Hg}$ and a pulse of $54\text{/min}$ . Physical examination reveals pale skin, sparse axillary and pubic hair, and delayed relaxation phase of deep tendon reflexes. No skin hyperpigmentation is noted.

Laboratory results:
Sodium: $133 \text{ mEq/L}$
Potassium: $4.1 \text{ mEq/L}$
Thyroid-stimulating hormone (TSH): $1.5 \text{ mU/L}$ (Reference: $0.4-4.0 \text{ mU/L}$ )
Free thyroxine (T4): $0.4 \text{ ng/dL}$ (Reference: $0.9-1.7 \text{ ng/dL}$ )

The physician plans to start levothyroxine for the patient's thyroid dysfunction. Which of the following is the most appropriate next step in management to perform prior to initiating this therapy?

A
Measure serum thyroid peroxidase antibodies
Assess morning serum cortisol levelsCevap
C
Obtain a magnetic resonance imaging of the brain
D
Measure early morning serum testosterone levels
E
Perform a high-dose dexamethasone suppression test

Cevap

Assess morning serum cortisol levels

The patient's laboratory results (low free T4 with an inappropriately normal TSH) indicate central hypothyroidism. His additional symptoms of fatigue, weight loss, hypotension, decreased libido, and morning headaches suggest panhypopituitarism (likely due to a pituitary macroadenoma). When initiating treatment for panhypopituitarism, it is critical to evaluate and treat adrenal insufficiency before starting thyroid hormone replacement. Levothyroxine increases the basal metabolic rate and enhances the hepatic clearance of glucocorticoids. If levothyroxine is administered to a patient with unrecognized and untreated adrenal insufficiency, it can precipitate a life-threatening acute adrenal crisis.

Adım Adım Çözüm

Analyze the thyroid laboratory results

The patient has a low free T4 with an inappropriately normal TSH

To distinguish between primary and central hypothyroidism

Synthesize the clinical findings

Symptoms of hypogonadism, hypotension, and headaches alongside central hypothyroidism strongly suggest panhypopituitarism

To identify the broad endocrine failure and the high likelihood of concurrent central adrenal insufficiency

Determine physiological requirements for treatment

Thyroid hormone replacement increases the basal metabolic rate and hepatic cortisol clearance, which requires verification of intact adrenal function first

To prevent precipitating an acute adrenal crisis and ensure immediate patient safety

Anahtar Kavram

In patients with central hypothyroidism or panhypopituitarism, adrenal function must be evaluated and adrenal insufficiency treated with glucocorticoids before initiating levothyroxine to avoid precipitating an acute adrenal crisis.

Soru

Cevap

Adım Adım Çözüm

Anahtar Kavram

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