The Tired Teenager

William E. Winter

A 15-year-old Caucasian male presented with chief complaints of weakness, fatigue, weight loss, and nausea that had developed slowly over the last 6 months. Nonspecific "tiredness" had been a problem for at least 9 months. His appetite was poor, but he did have a craving for table salt. A 15-lb (6.8-kg) unintended weight loss was reported over the last 9 months.

His past medical history was unremarkable. He had had no serious illnesses, no hos-pitalizations, and no surgeries. His immunizations were up-to-date. He took no chronic medications and had no allergies.

Review of his family history revealed that his 42-year-old mother developed Hashimoto thyroiditis at age 16. The maternal aunt had Graves disease that was diagnosed at age 22.

His review of systems was negative for polyuria, polydipsia, and nocturia. He suffered from "heat intolerance" and became easily dehydrated, although this could be treated by aggressive oral replenishment with Gatorade. He was never hospitalized for dehydration. He did not complain of headaches, cough, shortness of breath, or wheezing. While he did experience episodic nausea, there were no complaints of vomiting, diarrhea, or constipation.

Physical examination revealed a gaunt 15-year-old male in no acute distress. His height was 180 cm, and his weight was 50 kg. His body mass index (BMI) was 15 kg/m2. His vital signs were as follows: temperature = 37.1°C, pulse = 110 beats per minute at rest, respirations = 22 breaths per minute, blood pressure = 90/50 mm Hg. Repeat blood pressure measurement in the opposite arm revealed 88/43 mm Hg. HEENT examination was benign. Disks and fundi were normal. The neck was supple without masses, thyromegaly, or lymphadenopathy. The lungs were clear to auscultation and percussion. The abdomen was soft without masses or hepatosplenomegaly. Bowel sounds were present but reduced. He had Tanner IV genitalia and pubic hair. The pulses were weak (only 1+) and rapid in the upper and lower extremities. Capillary refill was delayed, suggesting reduced cardiac output. The patient's sallow skin displayed a mottled hyperpigmented in sun-exposed and non-sun-exposed areas. The skin creases were more deeply hyperpigmented as was a scar on his leg from a minor bicycle accident that occurred some years ago. The nailbeds and oral mucosal also exhibited hyperpigmen-tation. The lips were pale as were the nailbeds. Cranial nerves II-XII were grossly intact.

There were no focal neurologic deficits. Reflexes were 1+ and symmetrical in the upper and lower extremities.

The complaint of tiredness aroused an initially diverse differential diagnosis that included endocrine disorders, hematologic disorders, cardiovascular, infectious diseases, hepatic and renal disorders, as well as psychiatric disorders. The astute primary care physician noted several findings in the patient's history and physical examination that focused her workup on the possibility of Addison disease (i.e., primary adrenal insufficiency): salt craving, weight loss, borderline hypotension with tachycardia, and hyperpigmentation. Hypotension in adults is considered to be a systolic blood pressure of less than 90 mmHg or a blood pressure 40 mmHg less than their baseline blood pressure.

CBC, fasting basic metabolic panel (BMP), urinalysis (including the spot urine sodium concentration), and am (morning) cortisol were ordered. His CBC revealed a mild normocytic, normochromic anemia with a modestly increased eosinophil count but was otherwise unremarkable. His BMP is given below:

Reference

Value,

Interval,

Reference

Conventional

Conventional

Value,

Interval,

Analyte

Units

Units

SI Units

SI Units

Sodium

128 mEq/L

135-145

128 mmol/L

135 - 145

Potassium

5.8 mEq/L

3.5-5.0

5.8 mmol/L

3.5-5.0

Chloride

105 mEq/L

95-105

105 mmol/L

95-105

CO2, total

19 mEq/L

24-32

19 mol/L

24-32

Creatinine

1.3 mg/dL

0.5-1.2

114.9 mmol/L

44-106

Blood urea

26 mg/dL

10-20

9.3 mmol/L

3.6-7.1

nitrogen

Glucose

60 mg/dL

65-99

3.3 mmol/L

3.6-5.5

These studies were consistent with a (relatively) hyperchloremic, normal anion gap acidosis that most likely resulted from reduced mineralocorticoid activity based on the patient's hyponatremia and hyperkalemia. The urinalysis showed a urine specific gravity of 1.025 with a urine sodium of 40 mEq/L. This latter finding is pathologic as in the face of hyponatremia in the plasma, the urine sodium should generally be reduced to less than 10 mEq/L. Inappropriate urinary sodium loss was consistent with mineralocorticoid deficiency.

Hyperpigmentation together with mineralocorticoid deficiency were consistent with primary adrenal insufficiency. With deficient cortisol concentrations in the bloodstream, there is a lack of normal suppression of hypothalamic corticotrophin-releasing hormone (CRH) release leading to a subsequent elevation in adrenocorticotrophic hormone (ACTH; corticotrophin) release. The first 13 amino acids of ACTH share sequence identity with a-melanocyte-stimulating hormone (MSH). Thus a chronic elevation in ACTH can induce hyperpigmentation.

The patient's modest hypoglycemia was consistent with glucocorticoid insufficiency. Cortisol stimulates the production of gluconeogenic enzymes. The cortisol concentration was 5 mg/dL (138 nmol/L; am reference interval: 7-25 mg/dL; 193-690 nmol/L). This was consistent with glucocorticoid deficiency. Combined glucocorticoid and mineralocor-ticoid deficiencies can contribute to hypovolemia and hypotension, resulting in a compensatory tachycardia. A prerenal azotemia was recognized in the elevations in the both the plasma creatinine and BUN concentrations with a BUN: creatinine ratio of 20:1 (0.08: 1 mmol of urea/mmol of creatinine).

A confirmatory cosyntropin (Cortrosyn) stimulation test was performed:

Analyte

Cortisol Baseline + 30 min +60 min Baseline

Plasma renin activity (supine)

Value, Conventional Units

Reference Interval, Conventional Units

8 = change over baseline

Value, SI Units

166 nmol/L 248 nmol/L 304 nmol/L

Reference Interval, SI Units

The deficient peak cortisol and the deficient change in cortisol over baseline, of only 5 mg/dL, confirmed hypocortisolism (e.g., glucocorticoid insufficiency). The elevated renin result supported the diagnosis of mineralocorticoid insufficiency, and primary adrenal insufficiency was diagnosed.

A tuberculin skin test was placed to exclude tuberculus adrenalitis. The skin test was nonreactive 48 hours later. Testing for adrenal cell cytoplasmic autoantibodies (ACA) was positive, consistent with an autoimmune etiology for the patient's Addison disease.

In light of the family history of autoimmune thyroid disease, the finding of primary autoimmune adrenal failure as the etiology of the patient's Addison disease is not unexpected. Because multiple autoimmune endocrine diseases can occur in the same individual, the reference laboratory was asked to test the patient's serum sample for islet autoantibodies [e.g., islet cell cytoplasmic autoantibodies (ICA), glutamic acid decarboxylase autoantibodies (GADA), and insulin-associated 2-autoantibodies (IA-2A)], thyroperoxidase autoantibodies (TPOA), and steroidal cell autoantibodies (SCA). Whereas ICA, GADA, IA-2A, and SCA were negative, TPOA was strongly positive. Thyroid function studies revealed the following results:

Analyte

TSH Free T4

Value, Conventional Units

Reference Interval, Conventional Units

Value, SI Units

Reference Interval, SI Units

These data are consistent with the biochemical euthyroid state. The physician planned to repeat the TSH measurement on a yearly basis in an effort to detect thyroid gland insufficiency.

Based on the diagnosis of Addison disease, the physician prescribed replacement doses of oral glucocorticoids and an oral mineralocorticoid: 9-a-fluorohydrocortisone. During times of stress the patient was told to triple his glucocorticoid dose. He was also instructed concerning the parenteral injection glucocorticoids in the event of severe illness when he should also seek immediate medical care.

Over a period of a few weeks, his strength and vigor improved. Over 3 months, he gained 20 lb (9 kg). His nausea resolved. Repeat BMP displayed resolution of the patient's hyponatremia, hyperkalemia, hypoglycemia.

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