An evaluation is requested for a 48-year-old male who reports a pervasive sense of exhaust… — USMLE Step 2 CK

An evaluation is requested for a $48$ -year-old male who reports a pervasive sense of exhaustion, a $12\text{-kg}$ ( $26.5\text{-lb}$ ) weight gain, and significantly reduced libido over the past eight months. He has no significant past medical history and takes no medications.

Vital signs show a blood pressure of $96/60\text{ mmHg}$ and a heart rate of $54/\text{min}$ . Neurologic examination reveals bilateral temporal visual field deficits. Deep tendon reflexes exhibit delayed relaxation.

Laboratory studies yield the following results:

Laboratory Test	Result	Reference Range
Thyroid-stimulating hormone (TSH)	$1.4\text{ }\mu\text{U/mL}$	$0.4-4.0\text{ }\mu\text{U/mL}$
Free thyroxine (T4)	$0.5\text{ ng/dL}$	$0.9-1.7\text{ ng/dL}$
Total testosterone	$145\text{ ng/dL}$	$300-1000\text{ ng/dL}$
Luteinizing hormone (LH)	$1.5\text{ mIU/mL}$	$1.5-9.3\text{ mIU/mL}$

The physician determines that thyroid hormone replacement is indicated. Which of the following is the most critical step to perform prior to initiating this specific therapy?

Assessment of early morning serum cortisol levelsCevap
B
Serologic evaluation for anti-thyroid peroxidase antibodies
C
Immediate commencement of a low-dose levothyroxine regimen
D
Re-evaluation of thyroid status in three months without intervention
E
Administration of an exogenous testosterone formulation

Cevap

Assessment of early morning serum cortisol levels

The patient presents with signs of a pituitary macroadenoma (bitemporal hemianopsia) causing panhypopituitarism. The laboratory results show an inappropriately normal TSH in the setting of a low free T4, which is diagnostic of central (secondary) hypothyroidism. He also has central hypogonadism (low testosterone with a normal LH). In a patient with panhypopituitarism, central adrenal insufficiency is highly likely. Thyroid hormone increases the metabolic clearance of glucocorticoids. Initiating thyroid hormone replacement without first assessing and treating concomitant adrenal insufficiency can precipitate a potentially fatal adrenal crisis. Therefore, assessing the hypothalamic-pituitary-adrenal axis with an early morning serum cortisol (or ACTH stimulation test) is the most critical next step before starting levothyroxine.

Adım Adım Çözüm

Interpret the clinical presentation and physical exam.

Bitemporal hemianopsia combined with signs of hypothyroidism and hypogonadism strongly suggests a sellar mass (e.g., pituitary macroadenoma) causing compressive panhypopituitarism.

To localize the anatomical lesion responsible for the patient's multifaceted symptoms.

Analyze the laboratory data.

A low free T4 with an inappropriately normal TSH confirms central hypothyroidism. A low total testosterone with an inappropriately normal LH confirms central hypogonadism.

To differentiate between primary peripheral gland failure and central (secondary) endocrine failure.

Determine the necessary prerequisite prior to endocrine treatment.

In cases of panhypopituitarism, central adrenal insufficiency is highly likely and must be evaluated by checking cortisol levels before starting levothyroxine.

Thyroid hormone replacement increases the metabolic clearance of cortisol. If given to a patient with unrecognized adrenal insufficiency, it can precipitate a potentially fatal adrenal crisis.

Anahtar Kavram

In patients with central hypothyroidism (suggestive of panhypopituitarism), adrenal function must be evaluated and any adrenal insufficiency treated before initiating thyroid hormone replacement to avoid precipitating an acute adrenal crisis.

Soru

Cevap

Adım Adım Çözüm

Anahtar Kavram

Sık Yapılan Hatalar

Konular

Bu konudan daha fazla soru