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Difficulty: HardMonitoring and Treatment Evaluation

A 2828-year-old woman is evaluated in the psychiatric clinic for an acute manic episode characterized by a decreased need for sleep, grandiosity, and hyperverbosity. She is subsequently diagnosed with bipolar I disorder. Following a comprehensive discussion regarding mood stabilization, the physician decides to initiate therapy with lithium carbonate. In addition to monitoring serum medication concentrations, which of the following laboratory parameters must be evaluated at baseline and periodically monitored during long-term maintenance therapy with this agent? (Select exactly 33 options)

  1. Serum calciumAnswer
  2. Serum creatinineAnswer
  3. Thyroid-stimulating hormoneAnswer
  4. D
    Hepatic transaminases
  5. E
    Absolute neutrophil count

Answer

The required baseline and ongoing laboratory parameters for lithium therapy are serum calcium, serum creatinine, and thyroid-stimulating hormone.
The correct options identify the three main organ systems adversely affected by chronic lithium therapy: the parathyroid glands, the kidneys, and the thyroid gland. Lithium alters the calcium-sensing receptor threshold in the parathyroid gland, necessitating serum calcium monitoring to detect hyperparathyroidism. It is exclusively eliminated by the kidneys and can cause acute kidney injury, nephrogenic diabetes insipidus, and chronic tubulointerstitial nephropathy, requiring routine serum creatinine evaluation. Finally, it inhibits thyroid hormone synthesis, frequently leading to clinical hypothyroidism, which makes regular thyroid-stimulating hormone checks essential.

Step-by-Step Solution

1
Identify the prescribed medication and its organ-specific adverse effect profile.
The patient is starting lithium carbonate, which is known to affect the kidneys, thyroid gland, and parathyroid glands.
Pharmacologic monitoring is directly dictated by a drug's metabolism, excretion, and known end-organ toxicities.
2
Select the appropriate laboratory tests corresponding to lithium's toxicity profile.
Serum creatinine (for renal function), thyroid-stimulating hormone (for thyroid function), and serum calcium (for parathyroid function) are required.
These tests detect the development of chronic tubulointerstitial nephropathy, hypothyroidism, and hyperparathyroidism, respectively.
3
Differentiate lithium's monitoring requirements from those of other psychiatric medications.
Hepatic transaminases and absolute neutrophil count are excluded, as lithium does not cause hepatotoxicity or agranulocytosis.
Avoiding unnecessary testing prevents diagnostic confusion and adheres to standard-of-care guidelines.

Key Concept

Patients initiated on lithium therapy require baseline and periodic monitoring of serum creatinine (due to the risk of tubulointerstitial nephropathy), thyroid-stimulating hormone (due to the risk of hypothyroidism), and serum calcium (due to the risk of hyperparathyroidism).
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Topics

Monitoring and Treatment Evaluation

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