Endocrine case studies
1. A 34-year-old woman has new-onset hypertension. Her serum potassium level is 2.7 mmol/L. Initial hormone screening shows a plasma aldosterone (PA) of 55 ng/dL (normal [nl], 1–16) and a plasma renin (PR) of 0.1 ng/mL/hour (nl, 0.15–2.33). What is the probable diagnosis?
The presence of hypertension and hypokalemia suggests primary aldosteronism (Conn syndrome). The PA level is elevated, the PR is suppressed, and the PA/PR ratio is greater than 20, supporting this diagnosis. The diagnosis can be confirmed by demonstrating the failure of PA to suppress after volume expansion with intravenous saline or oral salt loading. The next step is to establish whether the cause is an aldosterone-producing adenoma or bilateral adrenal hyperplasia. Abdominal computed tomography (CT) should be performed. Because of her young age and very low serum potassium level, an aldosterone-producing adrenal adenoma is the most likely cause. The treatment for an aldosterone-producing adrenal adenoma is surgery. Spironolactone should be given to control blood pressure and to normalize the serum potassium preoperatively (see Chapter 27).
2. A 32-year-old business executive develops amenorrhea. She has not recently lost weight but states that her job is very stressful. Evaluation reveals the following laboratory results: serum estradiol = 14 pg/mL (nl, 23–145), luteinizing hormone (LH) = 1.2 mIU/mL (nl, 2–15), follicle-stimulating hormone (FSH) = 1.5 mIU/mL (nl, 2–20), prolactin = 6.2 ng/mL (nl, 2–25), thyroid-stimulating hormone (TSH) = 1.2 mU/L (nl, 0.5–5.0), and a serum pregnancy test is negative. A magnetic resonance imaging (MRI) scan of her pituitary gland is normal. What is the probable diagnosis?
The patient has secondary amenorrhea with low estradiol and gonadotropin levels. This clinical picture is most consistent with hypothalamic amenorrhea, which may occur in women who exercise excessively or have stressful jobs. The disorder results from reduced gonadotropin-releasing hormone (GnRH) pulse frequency in the hypothalamus. Treatment consists of stress management and, if menses do not resume, estrogen replacement therapy (see Chapter 47).
3. A nulliparous 48-year-old woman presents with symptoms of thyrotoxicosis. She has a modest, nontender goiter and no exophthalmos. She takes no medications and has had no recent radiology procedures. The following results are found on thyroid evaluation: free thyroxine (T4) = 3.5 ng/dL (nl, 0.8–1.8), TSH less than 0.1 mU/L, 24-hour radioactive iodine uptake (RAIU) = 1% (nl, 20%–35%), thyroglobulin = 35 ng/mL (nl, 2–20), and sedimentation rate = 10 mm/hour. What is the likely diagnosis?
The patient has clinical and biochemical thyrotoxicosis, but the RAIU is low. The differential diagnosis includes postpartum thyroiditis, silent thyroiditis, subacute thyroiditis, factitious thyrotoxicosis, and iodine-induced thyrotoxicosis. She has never been pregnant and denies medication use and recent iodine exposure. The nontender gland, elevated thyroglobulin, and normal sedimentation rate are most consistent with silent thyroiditis. A transient (1–3 months) thyrotoxic phase followed by a transient (1–3 months) hypothyroid phase is expected before the condition resolves; 20% of patients, however, remain hypothyroid. If symptomatic, the thyrotoxic phase is best treated with beta-blockers, and the hypothyroid phase can be managed, if necessary, with levothyroxine (see Chapters 33 and 35).
4. A 38-year-old man has coronary artery disease, xanthomas of the Achilles tendons, and the following serum lipid profile: cholesterol = 482 mg/dL, triglyceride (TG) = 125 mg/dL, high-density lipoprotein (HDL) cholesterol = 42 mg/dL, and low-density lipoprotein (LDL) cholesterol = 415 mg/dL. What is the probable diagnosis?
Significant elevations of total cholesterol and LDL cholesterol, normal TG, tendon xanthomas, and premature coronary artery disease are most consistent with a diagnosis of heterozygous familial hypercholesterolemia. This disorder is usually the result of deficient or abnormal LDL receptors or an abnormal apoprotein B-100 molecule. Aggressive lipid lowering with a combination of statins, ezetimibe, bile acid resins, and niacin is needed. In many cases, LDL apheresis is also indicated (see Chapter 6).
5. A 28-year-old man presents because of infertility. He is found to have small, firm testes and gynecomastia. Laboratory testing shows the following abnormalities: testosterone = 206 ng/dL (nl, 300–1000), LH = 88 mIU/mL (nl, 2–12), and FSH = 95 mIU/mL (nl, 2–12). What is the likely diagnosis?
The patient has hypergonadotropic hypogonadism with small firm testes and gynecomastia, which is most consistent with a diagnosis of Klinefelter syndrome. Such patients usually have a 47XXY karyotype. Androgen replacement therapy is the treatment of choice (see Chapters 43 and 44).
6. A 38-year-old nurse presents in a stuporous state; the blood glucose level is 14 mg/dL. Additional blood is drawn, and the patient is quickly resuscitated with intravenous glucose. Further testing on the saved serum reveals the following: serum insulin = 45 μU/mL (nl, <22), C-peptide = 4.2 ng/mL (nl, 0.5–2.0), and proinsulin = 7 pmol/L (nl, <5). A sulfonylurea screen is negative. What is the probable diagnosis?
The patient has hyperinsulinemic hypoglycemia. The differential diagnosis includes insulinoma, surreptitious insulin injection, and oral sulfonylurea ingestion. The elevated serum C-peptide and proinsulin levels are most consistent with an insulinoma. After an appropriate localizing procedure, surgical removal is the treatment of choice (see Chapter 53).
7. A 28-year-old woman develops amenorrhea. She has type 1 diabetes mellitus. Further testing reveals the following serum hormone values: estradiol = 15 pg/mL (nl, 23–145), LH = 78 mIU/mL (nl, 2–15), FSH = 92 mIU/mL (nl, 2–20), prolactin = 12 ng/mL (nl, 2–25), TSH = 1.1 mU/L; a pregnancy test is negative. What is the most likely diagnosis?
The patient has secondary amenorrhea with low estradiol and elevated gonadotropin levels. In a patient with another autoimmune disease (type 1 diabetes mellitus), the most likely diagnosis is premature ovarian failure resulting from autoimmune ovarian destruction. Hormone replacement therapy is the treatment of choice (see Chapter 47).
8. A 34-year-old woman presents with galactorrhea, amenorrhea, headaches, fatigue, and weight gain. Laboratory evaluation reveals the following: prolactin = 58 ng/mL (nl, 2–25), free T4 = 0.2 ng/dL (nl, 0.8–1.8), and TSH greater than 60 mU/L (nl, 0.5–5.0). She has an enlarged pituitary gland on MRI scan. What is the probable diagnosis?
The patient has moderately increased serum prolactin levels, pituitary enlargement, and severe primary hypothyroidism. Her entire clinical picture is most likely explained solely by the hypothyroidism, which is well known to cause secondary hypersecretion of prolactin and pituitary enlargement from thyrotroph hyperplasia. All abnormalities should resolve after adequate thyroid hormone replacement is established (see Chapters 20 and 47).
9. A 6-year-old girl has recently developed breast enlargement and some pubic hair. She has not complained of headaches and has had good health otherwise. Her older sister entered puberty at approximately 8 years of age. Her height is at the 90th percentile for her age, and her physical examination reveals Tanner stage III breast development and stage II pubic hair growth. Abdominal and pelvic examinations are normal. Laboratory tests show the following results: LH = 7 mIU/mL (nl, 2–15), FSH = 8 mIU/mL (nl, 2–20), prolactin = 6 ng/mL (nl, 2–25), TSH = 1.9 mU/L (nl, 0.5–5.0), and a normal pituitary MRI scan. Her bone age is 1.8 years ahead of the chronologic age. What is the probable diagnosis?
The patient has gonadotropin-dependent true precocious puberty. The etiology includes pituitary and hypothalamic tumors, but most cases in girls are idiopathic. The normal pituitary MRI points to a diagnosis of idiopathic precocious puberty. A long-acting GnRH analog should successfully arrest her premature development and allow her to enter puberty at a later, more appropriate time (see Chapter 43).
10. A 19-year-old man presents with excessive thirst and urination. Laboratory evaluation shows the following: serum glucose = 88 mg/dL, serum sodium = 146 mmol/L, serum osmolality = 298 mOsm/kg, and urine volume = 8800 mL/24 hour. A water deprivation test is performed, and it shows a urine osmolality of 90 mOsm/kg with no response to water deprivation and an increase in urine osmolality to 180 mOsm/kg after the administration of vasopressin. What is the likely diagnosis?
The patient has polyuria and polydipsia with maximally dilute urine. The differential diagnosis includes central diabetes insipidus, nephrogenic diabetes insipidus, and primary polydipsia. The lack of response to water deprivation and the more than 50% increase in urine osmolality after administration of vasopressin are most consistent with central diabetes insipidus. This may be caused by inflammatory or mass lesions in the hypothalamus but is often idiopathic. An MRI scan of the pituitary-hypothalamic region should be performed. The treatment of choice is intranasal or oral desmopressin (see Chapters 18 and 24).
11. A 25-year-old woman presents with a cushingoid appearance. The results of hormone testing are as follows: 24-hour urine cortisol = 318 μg (nl, 20–90), morning serum cortisol = 28 μg/dL (nl, 5–25), and morning plasma adrenocorticotropic hormone (ACTH) = 65 pg/mL (nl, 10–80). After an 8-mg oral bedtime dose of dexamethasone, the morning serum cortisol = 3 μg/dL. What is the probable diagnosis?
