A Difficult Case of HyperthyroidismSharry Kahlon University of Alberta, Edmonton, Alberta CanadaJune 2014

Case Presentation• 29 yo F with 1 month history of neck swelling, fatigue, tremor,

palpitations and insomnia, gritty eyes• Outpatient labs: Free T4 149, TSH< 0.03• Admitted with thyrotoxicosis

Case Presentation• Hospital course:

• PTU, Dex, Metoprolol• Lugol’s added when FT4 remained elevated• Thyroid scan- increased uptake consistent with Grave’s• Thyroid Ultrasound- enlarged, heterogenous, goitre• Discharged FT4= 45.7, Normal FT3 • Discharged on Methimazole 15 mg bid + Metoprolol

Case Presentation• < 1 week post discharge

• Non- Pruritic maculopapular rash trunk

Diagnosis?

Methimazole induced reaction

• Switched to PTU

Case Presentation• Symptoms and labs improved • FT4 15.1, Positive TRAB (28.04)• Scheduled for RAI + prednisone

• uptake scan I-131 done prior 87.7% • BhCG neg

Case Presentation• 1 week post ablation

• Symptomatic hyperthyroidism- palpitations, periorbital edema, tremor

• Enlarged, bulky, tender gland• FT4 56.6 FT3 21.6

• What is going on?

Case Presentation• 2 possibilities

• Thyroid gland is sequestering thyroxin• Radiation induced Thyroiditis

• Plan: • PTU, Metoprolol, Prednisone• Referred for surgery

Case Presentation• Over next 2-3 months- clinically and biochemically euthyroid• Awaiting surgery but started experiencing increasing

palpitations, tremors, N/V, weight loss 0.9 kg• FT4- 23.2, FT3- 8.5, TSH suppressed• What is going on??

Case Presentation• What test would you order next?

• BhCG Positive!• Patient had stopped OCP and this was unplanned pregnancy

NOW WHAT?

Thyroid and Pregnancy• Normal physiologic changes of pregnancy

• Increase in TBG increase in TOTAL T4/T3 to maintain normal FREE levels

• BhCG – stimulates thyroid receptor• Thyroid gland enlarges (but goitre still abnormal)• TSH decreases slightly in T1 in 20% F• Fetus relies on maternal Iodine supply throughout• Fetal synthesis of thyroid hormone starts at 12 wks

Thyroid and Pregnancy• Overt hyperthyroidism is uncommon in pregnancy - 0.1- 1% of

all pregnancies• Symptoms of pregnancy and hyperthyroidism overlap

Differential Diagnosis ?

Thyroid in Pregnancy

Pregnancy related

• BhHCG mediated• Gestational transient

thyrotoxicosis• Hyperemesis• Trophoblastic

Non-pregnancy related

• GRAVE’S• Thyroiditis• Adenoma• MNG• Factitious

Most common are BhCG mediated and Grave’s

Placental Transfer• TSH doe not cross placenta• Small amounts of T3/T4 cross placenta• TRH, iodine, TSH receptor Ab and TSI and anti thyroid drugs

cross placenta

Thyroid and Pregnancy• Dx is still based on suppressed TSH and elevated free hormone

levels• Trimester specific TSH ranges (mU/L):

• T1: 0.1-2.5• T2: 0.2-3• T3: 0.3-3

Pregnancy and Thyroid• Main issue is to differentiate Grave’s vs. BhCG• Features favoring Grave’s

• Ophthalmopathy, Goitre• + Thyrotropin receptor Ab- positive in 95% of Grave’s

• Features favoring HCG mediated• Postural hypotension, no prior hx of thyroid dx• Absence of goitre, tachycardia, ophthalmopathy

Consequences

Maternal

• Severe preeclampsia• Gestational HTN• Placental abruption• Postpartum Hemorrage

Fetal

• Spontaneous abortion• Prematuer labor• Low birth weight• Stillbirth• Placental transfer of

TRAb Fetal hyperthyroidism

• Good pregnancy outcomes in patients with good control• Poorly controlled thyrotoxicosis associated with thyroid storm( L&D)

Back to our case• 7 weeks pregnant• Thyroid vs pregnancy symptoms?• Symptomatic thyroid disease including eye symptoms, weight

loss• TSH receptor Ab – 636.4• FT4 = 23.2 ( at target for pregnancy)• PTU 600 mg daily 700mg daily

Back to our case• Medical Termination of Pregnancy• Eventual thyroidectomy and hypothyroid

Thank You

Pregnancy and Medications• Antithyroid drugs

• Cross placenta but do not cause fetal hypothyroidism unless high doses

• Target Ft4 at or just above ULN using smallest dose of ATD• Monitor FT4/TSH q4 weeks

Monitoring • Maternal Serum TRAb at 20-24 weeks• Neonatal monitoring –serial U/S

Pregnancy and Medications• PTU preferred in T1 and then switch for MMI• Teratogenicity is main concern

• MMI: embryopathy• PTU – Hepatoxicity

• Betablockers• Pregnancy class C • IUGR, Fetal bradycardia/hypoglycemia