Hypothyroidism

Definition

• Primary - intrinsic thyroid gland failure (up to 99% of all cases)
• Secondary/Central - lack of TSH stimulation from pituitary failure (rare)
• Tertiary - hypothalamic failure (very rare)

Epidemiology

• Affects 1-2% of women in the United States
• Subclinical hypothyroidism affects 4-10% of the general population
• Incidence of subclinical hypothyroidism in pregnancy: 5-8%
• Higher incidence in women (due to higher prevalence of autoimmune disease)
• Risk increases with age; no specific racial/ethnic predilection

Etiology

Primary Hypothyroidism (most common)

Secondary/Central Hypothyroidism

Clinical Features

General

• Fatigue, weight gain, cold intolerance
• Decreased sweating

Skin & Hair

• Dry, coarse, pale, cool skin
• Non-pitting edema (myxedema) - skin infiltration with glycosaminoglycans
• Dry, brittle hair; hair loss
• Lateral thinning of eyebrows (Queen Anne's sign)
• Yellow tinge (carotenemia)
• Thin, brittle nails

Neurologic

• Slow mentation and speech
• Impaired concentration and attention
• Lethargy, decreased short-term memory
• Agitation, psychosis ("myxedema madness")
• Seizures
• Ataxia, dysmetria
• Carpal tunnel syndrome
• Sensorineural hearing loss
• Peripheral neuropathy, paresthesias

Musculoskeletal

• Proximal myopathy, pseudohypertrophy
• Delayed relaxation of deep tendon reflexes ("hung-up reflexes" / pseudomyotonic)
• Polyarthralgias, joint effusions
• Acute gout or pseudogout

Cardiovascular

• Sinus bradycardia
• Long QT interval with increased ventricular arrhythmia risk
• Diastolic heart failure (delayed ventricular relaxation)
• Pericardial effusion (usually asymptomatic)
• Peripheral edema
• Decreased exercise capacity, dyspnea on exertion

Respiratory

• Dyspnea on exertion
• Obstructive sleep apnea
• Primary pulmonary hypertension (rare)

Gastrointestinal

• Constipation, ileus
• Gastric atrophy

Reproductive

• Oligomenorrhea and amenorrhea, OR menorrhagia
• Decreased fertility, early abortions
• Decreased libido, erectile dysfunction

Head/Neck

• Hoarseness, deep husky voice
• Macroglossia
• Periorbital swelling
• Goiter (in Hashimoto's)

Diagnosis

Laboratory Tests

• In secondary hypothyroidism: follow free T4, not TSH
• Subclinical hypothyroidism: TSH >4.5 but <10 mIU/L with normal fT4; patient may be asymptomatic

Additional Lab Abnormalities (overt hypothyroidism)

• Elevated cholesterol and triglycerides (decreased lipid clearance)
• Elevated creatine kinase (CK) - from myopathy
• Hyponatremia (SIADH-like state)
• Normocytic or macrocytic anemia
• Hyperprolactinemia (TRH stimulates prolactin)

Treatment

Levothyroxine (L-T4) - Drug of Choice

• Monitoring: Follow-up TSH approximately 6 weeks after any dose change (accounts for T4's 1-week half-life and TSH lag time)
• Once dose is stable, check TSH annually
• Take on empty stomach, 30-60 minutes before breakfast for best absorption

Combination T4 + T3 Therapy

• Not routinely recommended - the vast majority of controlled trials do not show superiority over T4 alone
• Desiccated thyroid (T4:T3 ratio ~4:1; 60 mg ≈ 65 µg levothyroxine) - occasionally preferred by patients; some report weight loss
• Liothyronine (synthetic T3) alone is less desirable for chronic use: shorter half-life (~20 h), more frequent dosing, transient T3 spikes above normal range
• A trial of combination T4+T3 may be reasonable if patient remains symptomatic with TSH in therapeutic range

Subclinical Hypothyroidism

• TSH >10 µU/mL: experts agree treatment is indicated
• TSH 4.5-10 µU/mL: treat if symptomatic or if pregnant

Pregnancy

• All pregnant patients with elevated TSH should be treated with levothyroxine
• Target TSH in the lower half of the normal range
• Check TSH every 4-6 weeks; dose requirements typically increase in first trimester
• Women planning pregnancy should optimize preconception TSH to reduce risk of first-trimester elevation

Myxedema Coma (Severe/Life-Threatening Hypothyroidism)

Recognition (Myxedema Coma Triad)

1. Hypothermia - temperature usually <36°C; <32°C is a poor prognostic sign; as low as 24°C reported; may be near-normal if infection is the precipitant
2. Altered mental status - lethargy and confusion to stupor/coma; agitation, psychosis, seizures ("myxedema madness")
3. Precipitating event - infection (pneumonia most common), MI, GI bleed, trauma, drugs (sedatives, narcotics), hyponatremia, hypoglycemia

Classic Profile

• Older woman in winter
• Known hypothyroidism or thyroidectomy scar
• Myxedema facies: puffy eyelids and lips, large tongue, broad nose
• Hypotension refractory to fluids and pressors unless thyroid hormone administered
• Slow, shallow respirations with hypercapnia/hypoxia

Management of Myxedema Coma

1. IV levothyroxine - 200-500 µg loading dose IV, then 50-100 µg/day
2. IV liothyronine (T3) - some centers add T3 for faster action (T3 is the active hormone)
3. Hydrocortisone 100 mg IV - empirically given before thyroid hormone, as undetected adrenal insufficiency can be precipitated by thyroid hormone replacement
4. Supportive care: intubation/ventilation, rewarming (passive preferred), IV fluids, treat precipitating illness
5. Avoid aggressive rewarming (can cause cardiovascular collapse)
6. Treatment often initiated based solely on clinical findings without waiting for labs

Special Considerations

Drugs That Cause or Worsen Hypothyroidism

• Amiodarone - contains ~37% iodine; can cause both hypo- and hyperthyroidism
• Lithium - inhibits thyroid hormone synthesis and release
• Interferon-alpha, checkpoint inhibitors (immune-related thyroid dysfunction)
• Iron, calcium supplements, cholestyramine - impair levothyroxine absorption (separate by at least 4 hours)

Hashimoto's Thyroiditis (Chronic Autoimmune Thyroiditis)

• Caused by TPO antibodies (primary) and anti-Tg antibodies attacking thyroidal stroma
• Progressive fibrosis → declining T4 production
• Average replacement dose in adults: 1.6 µg/kg/day L-thyroxine
• TSH followed annually to ensure adequate control
• Some patients have transient hyperthyroidism early ("Hashitoxicosis")

Key Takeaways

Orthopaedic History Writing

General Format

1. Biodata / Patient Profile
2. Chief Complaint (CC)
3. History of Present Illness (HPI)
4. Past Medical & Surgical History (PMH / PSH)
5. Drug & Allergy History
6. Family History
7. Personal & Social History
8. Systemic Review

1. Biodata / Patient Profile

• Name, Age, Sex - age and sex are diagnostically important (e.g. Paget's disease in elderly males; developmental dysplasia in female neonates)
• Occupation - critical in orthopaedics (laborer vs. sedentary worker; repetitive strain occupations)
• Dominant hand - for any upper limb complaint
• Address / Socioeconomic status - relevant for compliance, rehabilitation, and return to work
• Date of admission / referral
• Informant - patient, relative, bystander (especially in trauma cases)

2. Chief Complaint (CC)

"Pain in the right knee for 3 months" "Swelling of the left ankle following a fall 2 days ago" "Inability to walk since morning"

3. History of Present Illness (HPI) - The Core Section

A. Pain (SOCRATES mnemonic)

• Night pain, rest pain - bone tumour, infection, avascular necrosis, inflammatory arthritis
• Pain after sitting then improving with walking - ankylosing spondylitis ("gel phenomenon"), patellofemoral syndrome
• Pain on climbing stairs - patellofemoral syndrome
• Pain with squatting / locking - meniscal pathology
• Pain radiating below knee - lumbar disc herniation (sciatica), compartment syndrome

B. Swelling

• Onset: sudden (haemarthrosis - within 2 hours of injury, suspect ACL/fracture) vs. gradual (synovial effusion - 12-24 hours, suspect meniscal tear)
• Site and extent
• Fluctuant, tense, or bony hard
• Warmth and redness (infection, gout, inflammatory)
• Progressive vs. static vs. intermittent
• Any transillumination (ganglion, cyst)

C. Stiffness

• Time of stiffness: Morning stiffness >1 hour = rheumatoid/inflammatory arthritis; <30 min = osteoarthritis
• Which movements restricted (flexion, extension, rotation)
• Constant or intermittent

D. Deformity

• Was it present at birth (congenital) or acquired?
• Onset: sudden (fracture/dislocation) or gradual (progressive deformity - scoliosis, rickets)
• Fixed or correctable
• Progression over time

E. Instability / Giving Way

• Which joint and in what direction
• Precipitating activity
• Associated with pain, swelling, click, pop
• Frequency and effect on daily activities
• Distinguish true locking (mechanical block - meniscal tear, loose body) from pseudolocking (pain inhibition)

F. Locking

• True locking: joint locked in a position, cannot be fully extended/flexed - suggests meniscal tear, loose body
• Pseudolocking: pain inhibits movement
• Onset, frequency, self-reducing or requires manipulation

G. Weakness / Neurological Symptoms

• Muscle weakness - proximal (myopathy) vs. distal (neuropathy)
• Paraesthesia, numbness, tingling - dermatomal pattern (nerve root) vs. peripheral nerve distribution
• Bowel/bladder symptoms - red flag for cauda equina syndrome (requires emergency assessment)
• Gait disturbance - antalgic, Trendelenburg, foot drop

H. Functional Limitation

• Ability to walk (distance before pain, use of walking aids)
• Ability to climb stairs
• Activities of daily living (dressing, bathing, toilet)
• Work capacity (days off, modified duties)
• Sports and recreation
• Oxford Hip/Knee Score or similar functional scoring tools where applicable

I. Mechanism of Injury (for Trauma Cases)

• Nature of force: high-energy (RTA, fall from height) vs. low-energy (simple fall in elderly - fragility fracture)
• Direction of force: valgus/varus stress, rotation, axial loading
• Speed and impact (road traffic accident - speed of vehicles, seat belt use, airbag deployment)
• Position of limb at time of injury (e.g. knee flexed + axial load = PCL; knee hyperextended + valgus = ACL + MCL + medial meniscus - "unhappy triad")
• Specific mechanisms:
  • Non-contact deceleration with pop = ACL tear
  • Dashboard injury = PCL, posterior hip dislocation
  • Fall on outstretched hand (FOOSH) = distal radius fracture, scaphoid, clavicle
  • Axial load on spine = burst fracture
• Pre-injury state (loss of consciousness, chest pain, seizure before fall - indicates pathological vs. traumatic)
• Time elapsed since injury
• Bystander/paramedic report

"The amount of initial trauma and the energy involved in the injury should always be determined. High-energy traumatic collision sports and motor vehicle accidents are associated with an increased risk of bony defects." - Campbell's Operative Orthopaedics, 15th Ed.

4. Past Medical & Surgical History (PMH / PSH)

Medical History

• Previous orthopaedic problems in same or other joints
• Diabetes mellitus - affects wound healing, infection risk, neuropathy
• Rheumatoid arthritis, SLE, psoriasis - inflammatory arthropathies
• Osteoporosis - fragility fracture risk
• Gout / pseudogout - crystal arthropathies
• Tuberculosis - Pott's spine, tuberculous arthritis
• Malignancy - pathological fracture, metastatic disease
• Haematological disorders - haemophilia, sickle cell (avascular necrosis)
• Neurological conditions - Parkinson's (falls), cerebral palsy, polio
• Vascular disease - peripheral arterial disease, venous insufficiency
• Skin conditions - psoriasis (psoriatic arthropathy)

Surgical History

• Previous operations on the same limb/joint (prior fixation hardware, arthroplasty)
• Complications of previous surgery (infection, non-union, implant failure)
• Anaesthetic problems (malignant hyperthermia, difficult airway)
• Anticoagulant use - critical pre-operatively
• Blood transfusions, blood group

5. Drug & Allergy History

• Current medications: anticoagulants (warfarin, NOACs), antiplatelet agents (aspirin, clopidogrel), DMARDs, steroids (prolonged steroid use - osteoporosis, avascular necrosis, wound healing issues), bisphosphonates (atypical femoral fractures), fluoroquinolones (tendon rupture risk)
• Allergies: specify drug, nature of reaction (rash, anaphylaxis, GI intolerance), and distinguish true allergy from intolerance
• Latex allergy (important for surgical planning)
• Contrast dye allergy (relevant for arthrography, angiography)

6. Family History

• Congenital/hereditary conditions: clubfoot, dysplasia of the hip, Marfan syndrome, Ehlers-Danlos
• Inflammatory arthritis: rheumatoid, ankylosing spondylitis (HLA-B27 conditions)
• Metabolic bone disease: osteoporosis, Paget's disease
• Malignancy: bone tumours, multiple myeloma
• Haemophilia, sickle cell disease

7. Personal & Social History

• Occupation: type of work, physical demands, lifting requirements - for causation, prognosis, and return-to-work planning
• Dominant hand: upper limb injuries
• Sports and recreation: type, level (amateur/competitive), frequency
• Smoking: impairs fracture healing, wound healing, bone density
• Alcohol: falls risk, avascular necrosis (femoral head), osteoporosis
• Diet: calcium, vitamin D intake (bone health)
• Living conditions: stairs at home, social support (relevant for discharge planning)
• Weight / BMI: relevant for joint replacement candidacy and load on joints
• Menstrual history (in women): amenorrhoea, menopause status (osteoporosis risk)
• Nutritional status: malnutrition impairs bone and wound healing

8. Systemic Review

• Cardiovascular (hypertension, ischaemic heart disease - pre-op assessment)
• Respiratory (COPD, asthma - anaesthetic risk)
• Gastrointestinal (NSAID-induced GI effects)
• Urinary (retention - post-op, especially after spinal anaesthesia)
• Skin (wounds, pressure sores, psoriasis)

Summary: The Quick Orthopaedic Mnemonic

Special Points for Common Orthopaedic Presentations