17.3 Type 2 Diabetes & Thyroid Disease in Primary Care
Key Takeaways
- USPSTF recommends screening adults aged 35 to 70 who are overweight or obese, with BMI thresholds of 25 or 23 in Asian American individuals, repeating every 3 years if normal.
- Metformin is foundational first-line therapy, is weight-neutral or weight-reducing, carries no hypoglycemia risk as monotherapy, and requires annual vitamin B12 monitoring.
- Annual microvascular surveillance comprises dilated retinal examination, urine albumin-to-creatinine ratio with serum creatinine, and comprehensive foot examination.
- Hashimoto thyroiditis produces elevated TSH with low free T4 and anti-thyroid peroxidase antibodies, while Graves disease produces suppressed TSH with elevated free T4 and stimulating TSH receptor antibodies.
- Euthyroid status is required for normal ovulation and early fetal neurodevelopment, which makes thyroid assessment part of preconception care.
Last updated: September 2026
Type 2 Diabetes Mellitus: Screening, Diagnosis & Glycemic Targets
Type 2 Diabetes Mellitus (T2DM) is characterized by progressive peripheral insulin resistance accompanied by compensatory hyperinsulinemia and eventual pancreatic beta-cell secretory exhaustion.
USPSTF and ADA Screening Guidelines
- USPSTF Recommendation: Screen for prediabetes and type 2 diabetes in asymptomatic adults aged 35 to 70 years who are overweight or obese (BMI ≥25 kg/m², or ≥23 kg/m² in Asian American individuals). Repeat screening every 3 years if normal.
- ADA Criteria for Testing Asymptomatic Adults: Screen all individuals starting at age 35, or at any age in adults with BMI ≥25 kg/m² (≥23 kg/m² in Asian Americans) who possess at least one risk factor: first-degree relative with diabetes, high-risk racial/ethnic background (African American, Hispanic, American Indian, Asian American), history of Gestational Diabetes Mellitus (GDM), history of Polycystic Ovary Syndrome (PCOS), physical inactivity, hypertension (≥130/80 mm Hg), or dyslipidemia (HDL-C <35 mg/dL or triglycerides >250 mg/dL).
ADA Diagnostic Thresholds
Diagnosis requires two abnormal test results from the same sample or two separate test samples, unless the patient presents with classic hyperglycemic crisis or overt random hyperglycemia.
| Diagnostic Test | Normal | Prediabetes | Diabetes Mellitus |
|---|---|---|---|
| Fasting Plasma Glucose (FPG) | < 100 mg/dL (5.6 mmol/L) | 100 – 125 mg/dL (5.6–6.9 mmol/L) | ≥ 126 mg/dL (7.0 mmol/L) (fasting ≥8 hours) |
| Hemoglobin A1c (HbA1c) | < 5.7% (39 mmol/mol) | 5.7% – 6.4% (39–47 mmol/mol) | ≥ 6.5% (48 mmol/mol) (NGSP-certified assay) |
| 2-Hour 75-g Oral Glucose Tolerance (OGTT) | < 140 mg/dL (7.8 mmol/L) | 140 – 199 mg/dL (7.8–11.0 mmol/L) | ≥ 200 mg/dL (11.1 mmol/L) |
| Random Plasma Glucose | — | — | ≥ 200 mg/dL (11.1 mmol/L) + classic symptoms (polyuria, polydipsia, unexplained weight loss) |
Glycemic Targets
- Non-Pregnant Adults: Target HbA1c < 7.0% (53 mmol/mol) for most non-pregnant adults to minimize microvascular complications (retinopathy, nephropathy, neuropathy).
- Stringent Target (< 6.5%): Appropriate for newly diagnosed, younger individuals with long life expectancy and no cardiovascular disease, provided it can be achieved without clinically significant hypoglycemia.
- Less Stringent Target (< 8.0%): Indicated for patients with a history of severe hypoglycemia, limited life expectancy, advanced microvascular or macrovascular complications, or extensive comorbid medical conditions.
- Preconception Target: Women of reproductive potential should achieve an HbA1c < 6.5% (ideally <6.0%) prior to conception to minimize the risk of congenital cardiac and neural tube defects, spontaneous abortion, and macrosomia.
Comprehensive Diabetes Management & Microvascular Surveillance
Stepwise Pharmacotherapy
- Metformin (Biguanide): Foundational first-line pharmacotherapy alongside lifestyle interventions.
- Mechanism: Activates AMP-activated protein kinase (AMPK), inhibiting hepatic gluconeogenesis and increasing peripheral insulin sensitivity in skeletal muscle.
- Dosing: Initiate at 500 mg PO daily with the evening meal; titrate slowly by 500 mg weekly up to 1,000 mg PO BID (or 2,000 mg daily of extended-release formulation) to mitigate gastrointestinal side effects (nausea, abdominal cramping, loose stools).
- Clinical Profile: Weight-neutral or promotes modest weight loss; zero risk of hypoglycemia as monotherapy. Long-term use is associated with vitamin B12 deficiency; check annual serum B12 levels.
- Renal Thresholds: Contraindicated if eGFR < 30 mL/min/1.73m² due to risk of rare but fatal lactic acidosis. Do not initiate if eGFR is 30–44 mL/min/1.73m²; if already taking and eGFR falls to 30–44, reduce dose by 50%.
- GLP-1 Receptor Agonists (GLP-1 RAs; e.g., Semaglutide, Liraglutide, Dulaglutide):
- Mechanism: Mimic endogenous incretin glucagon-like peptide-1, stimulating glucose-dependent insulin secretion, suppressing postprandial glucagon, delaying gastric emptying, and promoting central satiety.
- Indications: Preferred add-on agent for patients with established ASCVD, high cardiovascular risk, or obesity. Produces substantial weight reduction and reduces major adverse cardiovascular events (MACE).
- Precautions: Contraindicated in patients with personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia type 2 (MEN 2). Discontinue before conception.
- SGLT-2 Inhibitors (e.g., Empagliflozin, Dapagliflozin):
- Mechanism: Inhibit sodium-glucose cotransporter-2 in the renal proximal convoluted tubule, blocking glucose and sodium reabsorption to promote urinary glucosuria and osmotic diuresis.
- Indications: Preferred in patients with diabetic kidney disease (proteinuria) or heart failure with reduced or preserved ejection fraction. Demonstrates robust nephroprotection and reduces heart failure hospitalizations.
- Adverse Effects: Increased incidence of vulvovaginal candidiasis and mycotic genital infections, urinary tract infections, volume depletion, and rare euglycemic diabetic ketoacidosis (euDKA) during periods of physiological stress or fasting.
Annual Triad of Microvascular Complication Surveillance
Certified nurse-midwives must coordinate or directly perform annual microvascular complication screenings for all individuals with type 2 diabetes:
- Diabetic Retinopathy: Annual dilated eye examination performed by an optometrist or ophthalmologist to detect microaneurysms, cotton-wool spots, hard exudates, or neovascularization.
- Diabetic Nephropathy: Annual spot urine albumin-to-creatinine ratio (uACR) and serum creatinine/eGFR. An elevated uACR (30–299 mg/g indicates microalbuminuria; ≥300 mg/g indicates macroalbuminuria) mandates initiation of an ACE inhibitor or ARB in non-pregnant patients to halt renal functional decline.
- Diabetic Peripheral Neuropathy: Annual comprehensive diabetic foot examination:
- Visual inspection of skin integrity, erythema, maceration, calluses, and deformities.
- Palpation of pedal pulses (dorsalis pedis and posterior tibial) to assess peripheral arterial perfusion.
- Loss of Protective Sensation (LOPS) Testing: Evaluated using the 10-gram Semmes-Weinstein monofilament applied perpendicularly to 4 to 10 plantar sites (hallux, 1st, 3rd, 5th metatarsal heads) until the nylon filament buckles.
- At least one additional neurological test: vibration perception using a 128-Hz tuning fork over the great toe interphalangeal joint, pinprick testing, or Achilles tendon reflex assessment.
Thyroid Disorders: Hypothyroidism vs. Hyperthyroidism
Thyroid dysfunction disproportionately affects women (female-to-male ratio of 5:1 to 8:1). Euthyroid physiology is critical for normal ovulatory function, fertility, and embryonic neurological development.
Clinical Comparison of Primary Thyroid Disorders
| Clinical Domain | Primary Hypothyroidism (Hashimoto Thyroiditis) | Primary Hyperthyroidism (Graves Disease) |
|---|---|---|
| Primary Etiology | Autoimmune lymphocytic infiltration and progressive destruction of thyroid parenchyma | Autoimmune synthesis of Thyroid-Stimulating Immunoglobulins (TSI) / TRAb that bind and stimulate TSH receptors |
| Key Symptoms | Profound fatigue, lethargy, cold intolerance, unexplained weight gain, severe constipation, dry skin, coarse brittle hair, periorbital edema | Heat intolerance, excessive diaphoresis, palpitations, resting tachycardia, tremor, nervousness/anxiety, weight loss with increased appetite, hyperdefecation |
| Menstrual Changes | Oligomenorrhea, amenorrhea, or heavy menstrual bleeding (menorrhagia) due to anovulation and hyperprolactinemia | Hypomenorrhea or secondary amenorrhea |
| Physical Exam | Bradycardia, hypothermia, slow hoarse speech, delayed relaxation phase of deep tendon reflexes (pseudomyotonia), diffuse firm painless goiter | Tachycardia, wide pulse pressure, warm moist velvety skin, fine hand resting tremor, proptosis/exophthalmos, pretibial myxedema |
| Diagnostic Labs | Elevated TSH + Low Free T4<br>(Subclinical: Elevated TSH + Normal Free T4)<br>Positive Anti-TPO antibodies (90%–95%) | Suppressed TSH (<0.01–0.1 mIU/L) + Elevated Free T4 and/or Free T3<br>Positive TSI / TRAb antibodies |
| First-Line Pharmacotherapy | Levothyroxine (synthetic T4): Full replacement dose ~1.6 mcg/kg/day (based on ideal body weight). Lower starting dose (25–50 mcg) in elderly or cardiac disease. | Thionamides (Antithyroid Drugs):<br>- Methimazole (MMI): Preferred in non-pregnant adults and trimesters 2 & 3.<br>- Propylthiouracil (PTU): Preferred in 1st trimester of pregnancy.<br>Symptomatic relief: Beta-blockers (propranolol, atenolol). |
| Drug Administration Rules | Take once daily in the morning on an empty stomach with full glass of water, 30–60 minutes before breakfast. Separate by ≥4 hours from calcium, iron, antacids, or PPIs. | Educate on signs of agranulocytosis (fever, severe sore throat). Instruct patient to stop medication immediately and obtain STAT CBC with differential. |
| Laboratory Surveillance | Monitor serum TSH every 6 to 8 weeks until euthyroid, then recheck annually or when symptoms change. | Monitor Free T4 and Total T3 every 4 to 6 weeks during active titration, maintaining free T4 at upper normal limit. |
| Pregnancy Adjustments | MANDATORY EMPIRIC DOSE INCREASE: Increase weekly levothyroxine dose by 25% to 30% (take 2 extra tablets weekly) immediately upon positive pregnancy test; recheck TSH q4w. | PTU in 1st trimester (minimizes teratogenic aplasia cutis/choanal atresia from MMI); switch to MMI in 2nd trimester (minimizes PTU fulminant hepatotoxicity). |
Test Your Knowledge
A 44-year-old woman with a 4-year history of type 2 diabetes mellitus presents for her routine annual primary care examination. Her current medications include metformin 1,000 mg twice daily. Her in-office HbA1c is 6.8%, blood pressure is 124/76 mm Hg, and BMI is 27 kg/m². When organizing her annual microvascular complication surveillance, which set of clinical evaluations must the certified nurse-midwife ensure is completed?
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B
C
D
Test Your Knowledge
A 31-year-old G1P0 at 5 weeks gestation presents to the clinic after obtaining a positive home pregnancy test. She has a history of primary hypothyroidism secondary to Hashimoto thyroiditis and has been maintained on a stable dose of levothyroxine 75 mcg orally once daily for the past 2 years. Her preconception TSH 3 months ago was 1.8 mIU/L (euthyroid). Which clinical instruction is the most appropriate initial management for this patient?
A
B
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D