A 27-year-old G1P0 at 12 weeks estimated gestational age presents for prenatal care. The patient says she has occasional nausea and vomiting and a few episodes of palpitations and diarrhea this last week. Physical examination is unremarkable, except for a heart rate of 145/min. Basic thyroid function tests are shown in the table below. Which of the following additional laboratory tests would be most useful in assessing this patient's condition? Thyroid-stimulating hormone (TSH) 0.28 mIU/L (0.3–4.5 mIU/L) Total T4 12 µg/dL (5.4–11.5 µg/dL)

Thyrotropin receptor antibodies (TRAb)

Total triiodothyronine (T3) levels

Thyroid peroxidase (TPO) antibodies

Thyroxine-binding globulin (TBG) levels

A 25-year-old pregnant woman at 28 weeks gestation presents with a headache. Her pregnancy has been managed by a nurse practitioner. Her temperature is 99.0°F (37.2°C), blood pressure is 164/104 mmHg, pulse is 100/min, respirations are 22/min, and oxygen saturation is 98% on room air. Physical exam is notable for a comfortable appearing woman with a gravid uterus. Laboratory tests are ordered as seen below. Hemoglobin: 12 g/dL Hematocrit: 36% Leukocyte count: 6,700/mm^3 with normal differential Platelet count: 100,500/mm^3 Serum: Na+: 141 mEq/L Cl-: 101 mEq/L K+: 4.4 mEq/L HCO3-: 25 mEq/L BUN: 21 mg/dL Glucose: 99 mg/dL Creatinine: 1.0 mg/dL AST: 32 U/L ALT: 30 U/L Urine: Color: Amber Protein: Positive Blood: Negative Which of the following is the most likely diagnosis?

Acute fatty liver disease of pregnancy

A 30-year-old woman presents for pregnancy counseling. She says she has an 8-week history of chronic diarrhea. She is also found to be intolerant to heat and has been significantly losing her hair. She denies any recent changes to her diet. The patient is afebrile and her vital signs are within normal limits. Her weight today is 45.0 kg (99.2 lb) which is 4.5 kg (10 lb) less than her weight during her last visit 2 months back. On physical examination, the patient is anxious and has a non-intention tremor. Significant exophthalmos is present. Laboratory findings are significant for a low TSH, elevated free T4 and free T3, and a positive thyroid stimulating immunoglobulin assay. She still wants to conceive a baby and asks for an appropriate treatment that is safe in pregnancy. Which of the following best describes the therapy she will most likely receive during her pregnancy for her thyroid disorder?

Antithyroid drugs (thionamides)

Thyroidectomy and thyroid replacement

A 31-year-old G3P2 who is at 24 weeks gestation presents for a regular check-up. She has no complaints, no concurrent diseases, and her previous pregnancies were vaginal deliveries with birth weights of 3100 g and 4180 g. The patient weighs 78 kg (172 lb) and is 164 cm (5 ft 5 in) in height. She has gained 10 kg (22 lb) during the current pregnancy. Her vital signs and physical examination are normal. The plasma glucose level is 190 mg/dL after a 75-g oral glucose load. Which of the listed factors contributes to the pathogenesis of the patient’s condition?

Insulin antagonism of human placental lactogen

Decrease in insulin gene expression

Production of autoantibodies against pancreatic beta cells

Decrease in insulin sensitivity of maternal tissues caused by alpha-fetoprotein

Point mutations in the gene coding for insulin

A 34-year-old woman, who had her first child 2 weeks ago, visits her family physician with concerns about constant fatigue and difficulty with breastfeeding. She was discharged from the intensive care unit after hospitalization for severe postpartum hemorrhage. Since then, she has tried multiple pumps and self-stimulation to encourage breast milk production; however, neither of these strategies has worked. Her blood pressure is 88/56 mm Hg and heart rate is 120/min. Which of the following best explains the underlying condition of this patient?

Pituitary infiltration by histiocytes

Pituitary stalk epithelial tumor

A 26-year-old primigravid woman at 25 weeks' gestation comes to the physician for a prenatal visit. She has no history of serious illness and her only medication is a daily prenatal vitamin. A 1-hour 50-g glucose challenge shows a glucose concentration of 167 mg/dL (N < 135). A 100-g oral glucose tolerance test shows glucose concentrations of 213 mg/dL (N < 180) and 165 mg/dL (N < 140) at 1 and 3 hours, respectively. If she does not receive adequate treatment for her condition, which of the following complications is her infant at greatest risk of developing?

Decreased amniotic fluid production

A 43-year-old man presents to the emergency department following a work-related accident in which both arms were amputated. The patient lost a substantial amount of blood prior to arrival, and his bleeding is difficult to control due to arterial damage and wound contamination with debris. His complete blood count (CBC) is significant for a hemoglobin (Hgb) level of 5.3 g/dL. The trauma surgery resident initiates the massive transfusion protocol and orders whole blood, O negative, which she explains is the universal donor. The patient receives 6 units of O negative blood prior to admission. He subsequently develops fever, chills, hematuria, and pulmonary edema. Several hours later, the patient goes into hemodynamic shock requiring the emergent administration of vasopressors. Of the following options, which hypersensitivity reaction occurred?

Type 2 hypersensitivity reaction

Type 1 hypersensitivity reaction

Combined type 1 and type 4 hypersensitivity reaction

Type 3 hypersensitivity reaction

Type 4 hypersensitivity reaction

As part of a clinical research study, microscopic analysis of tissues obtained from surgical specimens is performed. Some of these tissues have microscopic findings of an increase in the size of numerous cells within the tissue with an increase in the amount of cytoplasm, but the nuclei are uniform in size. Which of the following processes shows such microscopic findings?

Uterine myometrium in pregnancy

Liver following partial resection

Cervix with chronic inflammation

A 38-year-old woman with type 1 diabetes for 20 years presents with diabetic ketoacidosis. She is treated and recovers. Six months later, she develops progressive fatigue, nausea, and hyperpigmentation. Laboratory studies show morning cortisol 3 μg/dL, ACTH 180 pg/mL, TSH 8.2 mIU/L, free T4 0.6 ng/dL, and positive anti-thyroid peroxidase antibodies. She also has positive 21-hydroxylase antibodies. Her 12-year-old daughter was recently diagnosed with type 1 diabetes. Evaluate the pathologic process and most critical monitoring recommendation for the daughter.

Autoimmune polyglandular syndrome type 2; screen daughter for adrenal antibodies and thyroid function annually

Multiple endocrine neoplasia syndrome; screen for pheochromocytoma and medullary thyroid cancer

Schmidt syndrome with isolated sporatic occurrence; routine diabetes management only for daughter

Autoimmune polyglandular syndrome type 1; screen for mucocutaneous candidiasis and hypoparathyroidism

Secondary endocrine failure from diabetes complications; optimize glycemic control in daughter

Endocrine disorders in pregnancy for USMLE Step 3: High-Yield Pathology Lessons

Gestational Diabetes - Sweet Baby, Sour Mom

Pathophysiology: Human placental lactogen (hPL) and other placental hormones ↑ insulin resistance in the mother.
Screening & Diagnosis: Standard two-step approach.

Pathophysiology of Gestational Diabetes and Fetal Macrosomia

Maternal Risks: ↑ risk of preeclampsia, C-section, and future Type 2 DM.
Fetal Risks: Macrosomia, neonatal hypoglycemia, polycythemia, respiratory distress.

⭐ High-Yield: Fetal macrosomia results from fetal hyperinsulinemia (insulin as a growth factor). After birth, persistent hyperinsulinemia with loss of maternal glucose supply causes profound neonatal hypoglycemia.

Thyroid Disorders - Bumps, Babies, & Butterflies

Physiologic Changes: ↑ Estrogen → ↑ Thyroxine-binding globulin (TBG) → ↑ Total T4. hCG can weakly stimulate TSH receptors, causing transient hyperthyroidism.
Maternal Hypothyroidism: Key risk is impaired fetal neurodevelopment (cretinism). Requires ↑ levothyroxine dose.
Maternal Hyperthyroidism (Graves'):
- 📌 Propylthiouracil (PTU) for Primary (1st) trimester.
- Methimazole for 2nd/3rd trimesters to avoid PTU hepatotoxicity.

⭐ TSH-receptor antibodies (TSI) are IgG and can cross the placenta, causing fetal/neonatal thyrotoxicosis.

Preeclampsia & HELLP - When Pregnancy Gets Pressured

Preeclampsia: New-onset hypertension (BP >140/90 mmHg) after 20 weeks gestation PLUS proteinuria or signs of end-organ damage.
Pathophysiology: Defective spiral artery remodeling → placental ischemia → release of anti-angiogenic factors (e.g., sFlt-1) → systemic endothelial dysfunction.
HELLP Syndrome: A severe manifestation of preeclampsia.
- Hemolysis (schistocytes on smear, ↑LDH)
- Elevated Liver enzymes (AST, ALT)
- Low Platelets (<100,000/μL)
Management:
- Definitive cure: Delivery of the placenta.
- Seizure prophylaxis: Magnesium sulfate (MgSO₄).
- BP control: Hydralazine, Labetalol, Nifedipine.

⭐ The definitive treatment for preeclampsia/HELLP syndrome is delivery of the fetus and placenta, which resolves the underlying pathology.

Preeclampsia: Spiral Artery Remodeling & Pathophysiology

Pituitary & Adrenal Issues - The Other Endocrine Players

Sheehan Syndrome: Postpartum pituitary necrosis due to severe hemorrhage & hypotension.
- Presents with failure to lactate (↓ prolactin), amenorrhea, adrenal insufficiency (↓ ACTH), and hypothyroidism (↓ TSH).
- Onset is often gradual.
Lymphocytic Hypophysitis: Autoimmune pituitary inflammation, usually in late pregnancy or postpartum.
- Can mimic a pituitary adenoma, causing headaches, visual defects, and hypopituitarism.
Adrenal Insufficiency (Addison's): Requires increased glucocorticoid doses during pregnancy and stress-dose steroids for labor to prevent adrenal crisis.

⭐ Failure to lactate is the most common initial sign of Sheehan syndrome.

Lymphocytic Hypophysitis: Stages, Symptoms, and Outcomes

High‑Yield Points - ⚡ Biggest Takeaways

Gestational diabetes is driven by hPL-induced insulin resistance; screen at 24-28 weeks.

Maternal hyperglycemia → fetal hyperinsulinemia → macrosomia & neonatal hypoglycemia.

hCG stimulates TSH receptors, raising total T4; free T4 and TSH levels remain normal.

Graves' disease often improves during pregnancy; maternal anti-TSH receptor antibodies can cause fetal thyrotoxicosis.

Postpartum thyroiditis presents as transient hyperthyroidism, often followed by a hypothyroid phase.

Sheehan syndrome is postpartum pituitary necrosis causing failure to lactate and hypopituitarism.

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