Nurse Practitioner Chronicles

  Fatigue Workup in Childbearing Women: Not a Fishing Trip Four tests. That’s the starting line: CBC, ferritin, TSH, pregnancy test. Not a 30-tube rainbow draw. “I'm just so tired all the time.” It's one of the most common complaints in primary care, and in women of childbearing age, the differential is simultaneously broad and predictable. The temptation is to order everything—a CMP, CBC, iron studies, B12, folate, vitamin D, cortisol, ANA, Lyme, EBV, celiac panel, ferritin, TSH, free T4, testosterone—and hope something lights up. That's not a workup. That's a fishing trip. And fishing trips catch incidental abnormalities that generate more tests, more anxiety, and no answers. This post makes the case for a disciplined, stepwise approach. The Core Four: Start Here, Every Time The First-Line Panel CBC : Anemia is the most common lab-identifiable cause of fatigue in this population. Look at hemoglobin AND MCV (microcytic = iron deficiency until proven otherwise). Ferriti...

  Thyroid Function Tests: TSH, Free T4, Free T3—and When You Actually Need Each One TSH is almost always enough. Free T3 is almost never needed. And sick euthyroid syndrome fools everyone. This post complements the thyroid antibody workup from earlier in the series. That post covered  which  antibody to order when you suspect autoimmune thyroid disease. This one covers the function tests—TSH, free T4, and free T3—and the interpretation patterns that trip up clinicians daily. The Hierarchy: TSH First, Always TSH is the single best screening test for thyroid dysfunction in outpatient primary care. The pituitary amplifies small changes in thyroid hormone levels, making TSH far more sensitive than direct hormone measurement. A normal TSH essentially rules out primary thyroid disease in an outpatient setting. TSH Free T4 Free T3 Interpretation ↑ High ↓ Low — Overt hypothyroidism.  Treat with levothyroxine. ↑ High Normal — Subclinical hypothyroidism.  Repeat in 6–12 w...