IADPSG 2016
Update on Gestational Thyroid Disease Aidan McElduff The Discipline of Medicine, The University of Sydney IADPSG 2016
DISCLOSURES and AIM Nil to disclose Aim: to provide an overview 2017 Guidelines of the American Thyroid Association
Normal state The system is in equilibrium.
Pregnancy Beta hcg is secreted in large amounts, has TSH like activity, and stimulates the thyroid gland Negative feedback is directed to the pituitary and TSH secretion is inhibited. There is no negative feedback to the placenta. NOT equilibrium normal range?
. Moving targets Glinoer D Endo Reviews 1997;18: 404-33 Novo RCPA 08 2017
hcg: a dose response In a study of 63 women hcg concentrations >200,000 IU/L, TSH was suppressed ( 0.2 mu/l) in 67% If >400,000 IU/L, TSH was suppressed ( 0.2 mu/l) in 100% of women Thyroid 2009;19:863-8
Results of hcg stimulation the thyroid gland increases in size by 10% in iodine replete countries, but by 20%- 40% in areas of iodine deficiency daily iodine requirement increase 50% production of the thyroid hormones, T4 and T3, increases by nearly 50%, IF everything normal ie adequate thyroidal reserve
THYROID RESERVE Anti TPO/TG Abs in up to ~20% of women Identifies risks during and after pregnancy Other causes: 131 I, thyroid surgery, iodine deficiency The concept of at risk
TFTs: TSH Falls < lower than normal* in 15,10,5% of women in 1 st, 2 nd, 3 rd trimesters (0.1-0.2) Endocr Rev 1997;18:404-33 but the fall at upper end of the non pregnant normal range is not clear. It varies between ethnic/racial groups (0.5-1.0) Use ~ 4 IU/L if local unavailable There are assay variations (Multiples of Median suggested by some)
TFTs: free T4 Is lower in routine assays The use of population based, trimesterspecific reference ranges remains the best way to handle this issue.
Hypothyroidism Gets worse Established, increase thyroxine (patient initiated with pregnancy test) New appearance common especially in at risk group (monitor or treat? eg Ab+ve women with previous miscarriage) NOT the same as Isolated Hypothyroxinaemia Rx Thyroxine targeting TSH < 2.5 miu/l (not thyroid cancer, same as preconception) Monitor 4 weekly until midgestation and once ~30 weeks
Hypothyroidism no other maternal or fetal testing recommended apart from TFTs except with Graves disease effectively treated with 131 I ablation or surgical resection requires TRAb monitoring Reduce thyroxine (re-asses in new) post partum, repeat TFTs at 6 weeks
Isolated Hypothyroxinaemia Free thyroxine in lower 2.5-5 centile with normal maternal TSH Not treated
New Hyperthyroidism Low TSH (brings to attention) Measure free thyroxine or total thyroxine and free T3 Identify cause: history, physical exam, TRAb, (hcg me),?us, NO radionucleotide scans PD Gestational Transient Thyrotoxicosis (hcg dependant) Rx support (esp rehydration), possibly beta blockers, no anti-thyroid medication GTT can trigger Graves or nodules
Pre-existing Hyperthyroidism Graves, nodules, thyroiditis, overtreatment or factitious, rare stuff Counselling on Dx then pre a planned pregnancy Stabilise (2 sets TFTs (in reference range) 1 month apart) Counsel Therapy, no right answer, ablative or medical
Pre-existing Hyperthyroidism Ablative: surgery worsening hypothyroid risk persistent TRAb plus with 131 I slower onset avoid pregnancy (6 months) Medical PTU liver problems in mother PTU congenital malformations (mild) Neomercazole rare congenital malformations
Pre-existing Hyperthyroidism Graves disease ameliorates PTU neomercazole Target free T4 ~ ULN Monitor 4 weekly NO block and replace Monitor TRAb (varies) Thyroidectomy 2nd trimester
Post Partum Graves relapse common Post partum thyroiditis very common Autoimmune ~50% in Ab+ve women Textbook: hyper followed by hypo (25%) Short (10-20%) and long term (50% at 8 years) hypothyroidism common
Thyroid nodules As per outside pregnancy with patient preference re timing Similarly for thyroid cancer unless medullary or anaplastic or aggressive (LNs/ growing)
Iodine Deficiency: A comment Novo 08
Recommendation 4 Median urinary iodine concentrations can be used to assess the iodine status of populations, but single spot or 24-hour urine iodine concentrations are not a valid marker for the iodine nutritional status of individual patients. (Strong recommendation, High quality evidence) 2017 Guidelines of the American Thyroid Association
Recommendation 97 All patients seeking pregnancy, or newly pregnant, should undergo clinical evaluation. If any of the following risk factors are identified, testing for serum TSH is recommended. A history of hypothyroidism/hyperthyroidism or current symptoms/signs of thyroid dysfunction Known thyroid antibody positivity or presence of a goiter History of head or neck radiation or prior thyroid surgery Age >30 years Type 1 diabetes or other autoimmune disorders History of pregnancy loss, preterm delivery, or infertility Multiple prior pregnancies ( 2)
Recommendation 97 Family history of autoimmune thyroid disease or thyroid dysfunction Morbid obesity (BMI 40 kg/m2) Use of amiodarone or lithium, or recent administration of iodinated radiologic contrast Residing in an area of known moderate to severe iodine insufficiency (Strong recommendation, Moderate quality evidence) Pituitary disease (TFTs)
The END IADPSG 2016
from Public Health Nutrition 2007 original Arch Latinoamericanos de Nuticion 1970;20:309!!! late morning urine sample Endemic goitre threshold SOMANZ 08 SOMANZ 08
from Public Health Nutrition 2007 original European J Clin Nutrtion 1999;53:401 SOMANZ 08
Recommendation 1 When possible, population-based trimester-specific reference ranges for serum TSH should be defined through assessment of local population data representative of a healthcare provider s practice. Reference range determinations should only include pregnant women with no known thyroid disease, optimal iodine intake, and negative TPOAb status. (Strong recommendation, Moderate quality evidence)
The END IADPSG 2016
IADPSG 2016
IADPSG 2016
Update on Gestational Thyroid Disease Aidan McElduff The Discipline of Medicine, The University of Sydney
Update on Gestational Thyroid Disease Aidan McElduff The Discipline of Medicine, The University of Sydney