Thyroid disease in pregnancy: A review of diagnosis, complications and management

Table 1 Recommended values of thyroid stimulating hormone for each trimester

First trimester	0.1-2.5 mIU/L
Second trimester	0.2-3.0 mIU/L
Third trimester	0.3-3.0 mIU/L

Table 2 Studies of subclinical hypothyroidism in pregnancy

Ref.	Design	Method	Result	Conclusion
Pop et al[23], 1999	Cohort study	220 children were evaluated at 10 mo of age. Maternal TSH, FT4 and TPO antibodies were measured at 12 and 32 wk of pregnancy	Children of women with FT4 levels less than the 5th and 10th centiles at 12 wk had lower scores on the Bayley Psychomotor Development Index at 10 mo. No differences were found at 32 wk	FT4 < 10% ile at 12 wk is a risk factor for impaired psychomotor development in offspring
Haddow et al[7], 1999	Retrospective	62 women with high TSH	Children of these women did less well on 15 tests of intelligence. Average decrease in IQ was 4 points	Undiagnosed hypothyroidism adversely affects the fetal neurodevelopment
Henrichs et al[8], 2010	Population based cohort	Women with normal TSH and FT4 < 5th and 10th centile. Expressive vocabulary of children was evaluated by mother at 18 and 30 mo	Maternal TSH not related to outcome. Both mild and severe low FT4 associated with higher risk of expressive language delay at all ages. Severe had higher risk of nonverbal cognitive delay	Maternal low FT4 is a risk factor for early childhood cognitive delay
Lazarus et al[11], 2012	Randomized prospective	Women in screening group were tested and treated Women in the control group had stored samples which were tested after delivery and received no treatment during pregnancy	No difference in cognitive function between the two groups at 3 yr of age	Screening and treatment for hypothyroidism did not improve neurodevelopmental outcomes in the offspring
Ghassabian et al[24], 2014	Cohort	3727 mother-child pairs with prenatal thyroid fxn tests before 18 wk. FT4 < 5% of normal. MRI of childrens brains and IQ test at age 6 yr	Children of mothers with low FT4 scored 4.3 points lower on nonverbal IQ test. No morphologic difference by MRI	Maternal hypothyroxinemia has adverse effect on children’s non-verbal IQ at school age
Chen et al[13], 2015	Prospective	106 babies born to mothers with SCH and 106 babies born to euthyroid mothers	Babies from both groups had similar scores on the Gesell development test	No neurodevelopmental deficit detected up to 24 mo in babies of mothers with SCH

TSH: Thyroid stimulating hormone; TPO: Thyroid peroxidase; FT4: Free T4; SCH: Subclinical hypothyroidism; MRI: Magnetic resonance imaging; IQ: Intelligence quotient.

Table 3 Diagnosis and treatment of thyroid disease in pregnancy

	TSH	FT4	FT3	Rx	Goal of treatment
Hypothyroid	↑	↓	↓	Levothyroxine starting dose 1-2 mcg/kg daily	Keep TSH normal range
Hyperthyroid	↓	↑	↑	PTU 50-150 mg TID in first trimester methimazole 10-40 mg BID or TID after first trimester	Keep FT4 high normal “watch for agranulocytosis”

TSH: Thyroid stimulating hormone; FT3: Free T3; FT4: Free T3; BID: Twice daily; TID: Three times daily; PTU: Propylthiouracil.

Table 4 Six steps for treatment of thyroid storm

1 Admit to intensive care unit	IV fluids and watch electrolytes
2 Tylenol 650 mg q6 h	For hyperpyrexia
3 Loading dose of 1000 mg PTU orally then 200 mg orally q6 h; alternate dosing 300 mg PTU q6 h	Will block synthesis of T3 and T4
4 Iodine supplementation 10 drops of Lugol’s solution q8 h OR 1 g sodium Iodide IV q8-12 h Iodine allergy use lithium carbonate 300 mg PO q6 h	Blocks release of hormone from the thyroid gland
5 Hydrocortisone 50-80 mg q8 h for 3 doses OR Dexamethasone 2 mg IV q6 h for 4 doses	To block peripheral conversion of T4 to T3
6 Beta blocker Labetolol 300 mg TID may increase to a max dose of 800 mg TID but watch blood pressure	To control the tachycardia – use cautiously in heart failure

PTU: Propylthiouracil; TID: Three times a day.

Table 5 Frequency of antenatal surveillance

	Ultrasound	Antenatal testing (Nonstress test or Biophysical Profile)
Hyperthyroid	Monthly	Twice weekly if poorly controlled
Hypothyroid	No recommendation Consider monthly	No recommendation