Thyroid Disease In Pregnancy

Clinical description

Although thyroid disease in pregnancy is not common, it is associated with perinatal morbidity and mortality.

Hyperthyroidism, when untreated or uncontrolled, is associated with spontaneous abortion, stillbirth, IUGR, preterm labour, preeclampsia and cardiomyopathy.

Hyperthyroidism is usually due to Graves disease (thyroid-stimulating antibodies).

Thyroid storm is a life-threatening emergency that is typically triggered by infection, surgery or labour.

The most common aetiologies of hypothyroidism are Hashimoto thyroiditis, postablation or thyroidectomy, primary atrophic hypothyroidism and iodine deficiency.

Because maternal subclinical hypothyroidism has been associated with neuropsychological decrements in children, consider screening pregnant women with the following for thyroid disease:

• Personal or family history of thyroid disease
• Signs/symptoms suggestive of goitre or hypothyroidism
• Type 1 diabetes
• Personal history of other autoimmune disorders

Diagnosis/Management All cases of suspected thyroid disease should be referred to the Central Hospital for management.

Hypothyroidism History/Exam: Fatigue, muscle cramps, hair loss, inability to concentrate, constipation and dyspnea.

Investigations: Increased TSH, Decreased free T4 (fT4), Decreased FTI

Treatment

Goals of therapy:

• TSH at or slightly below normal
• fT4 at the upper limit of normal

Pre-established hypothyroidism:

• Levothyroxine daily dose usuallyincreases in pregnancy.
• Send blood for fT4 and TSHevery trimester so that dose canbe changed to maintain goals of therapy.
• Send blood more frequently (but≥ 4 wks apart) if indicated.

New diagnosis of hypothyroidism:

• Start with levothyroxine 50-100mcg PO OD and increase every 4wks to achieve goals of therapy(most

require 150-300 mcg PO OD).

• Send blood for fT4 and TSHevery 4 wks until goals oftherapy are attained and thenevery 8-12 wks.

Hyperthyroidism History/Exam: Tachycardia, thyromegaly, failure to gain weight, heat intolerance, fatigue, palpitations and warm moist skin.

Investigations:Decreased TSH, Increased fT4

Treatment

• Start with PTU 100-150mg PO TDSuntil fT4 is at upper limit of normal.
• Maintain with PTU 50-150mg PO OD.

Clinical description

• Stop PTU for jaundice, fever, chills,sore throat, petechiae or bleedinggums; switch to methimazole 5-

10mgPO TDS.

• Send blood for fT4 or FTI every 4 wksthroughout pregnancy.
• Follow every 1-2 wks; keep pulse <100 and monitor weight gain.
• If indicated, then propranolol 10-40mg PO every 6-12 hours.
• For preterm labour, do not treat withbeta-mimetics and use magnesiumsulphate with caution due to

possiblevolume overload andcardiomyopathy.

Thyroid storm History/Exam: Tachycardia >150 bpm, fever, altered mental status, hypertension, diarrhoea, nausea, vomiting, severe dehydration, and fetal tachycardia +/- high output cardiac failure and arrhythmia.

Investigations: Leukocytosis, electrolyte abnormalities (i.e. hypercalcaemia), elevated LFTs, increased fT4 and fT3.

Management: Manage in SOU or ICU.

The general main focus is to prevent hypothyroidism, with the possible serious consequences for the baby.