SUBCLINICAL HYPERTHYROID IN PREGNANCY
QUESTION- I have a 29 year old lady, 8 weeks pregnant, referred by her obstetrician for suppressed TSH. No family history of thyroid disorders. Asymptomatic regarding hyperthyroid symptoms.
I checked her thyroid autoantibodies ---anti TPO anti antibody, anti thyroglobulin antibody, TSH -receptor antibody --all of which are within normal reference range. FT4 and FT3 are also normal with suppressed TSH. Inflammatory markers , i.e CRP and ESR normal.
How should this person's suppressed TSH managed ? Should she be started on propylthiouracil ? Should you just wait and watch ? Dr Sagarika Mukherjee, Consultant in Diabetes & Endocrinology, Kolkata
RESPONSE-The TSH is often quite low (ie below the normal non pregnant reference range) during the first trimester. This is due to the presence and TSH like action of hCG which rises during the first trimester to a maximum around 12-14 weeks. Hence your patent is almost certainly normal from the thyroid point of view and does not require therapy. Even if she continues to show subclinical hyperthyroidism through pregnancy there is no evidence (from a very large study) that this is detrimental to mother or fetus. John Lazarus, MD
RAI THERAPY DURING KIDNEY DIALYSIS
QUESTION-- I wanted to know your recommendations regarding dosing a patient with hyperthyroidism with radioactive iodine who has ESRD on hemodialysis 3 days a week. How much would you give and when should it be given in timing with dialysis? Should patient be dialyzed more frequently following treatment?
Gay M. Story, M.D., FACE
RESPONSE-There is only one report on radioiodine treatment for hyperfunctioning nodular goiter in a patient on dialysis. Larger experience is with thyroid cancer. In this context, RAI activity in the order of 100 mCi are safe. The dose must be administered soon after HD and the HD is repeated after 24, 48, 72 and 96 hours. In a patient with hyperthyroidism I would reduce the dose of RAI by 50% because the retention time will be longer and the renal clearance is of course reduced. Thus, if you use standard doses of 15 mCi (as in Italy), I would give 7-8 mCi. There should be no toic effects from radioiodine. Sincerely, Furio Pacini MD
HOW IS THYROGLOBULIN PROCESSED IN THE THYROID? 8/7/2017
QUESTION- I am a second year medical student and I just had a question about thyroglobulin.After T3 and T4 are cleaved off by lysosomes, what happens to the remaining structure? Does it get recycled through the RER to become thyroglobulin again or ? Thank you so much for your time. Stephanie Tan=
RESPONSE--Hi StephaniE. Iodinated thyroglobulin undergoes intralysosomal degradation that may involve two main steps: an early and selective proteolytic cleavage leading to the release of T3 and T4, and a delayed nonselective proteolysis for extensive degradation of the remaining peptides of Tg.
Tg molecules with no or low hormone content present in early apical endosomes are recycled back to the follicular lumen. Some Tg molecules are also transported to the basolateral membrane via transcytotic vesicles (this process accounts for the presence of non-iodinated Tg in the plasma).
This is a very simplified answer to your question. You can find more explanation and related publications on the mechanisms of Tg endocytosis in the chapter Thyroid hormone synthesis and secretion in www.Thyroidmanager.org. Hoping this will help you.
Françoise Miot PhD, IRIBHM, Université Libre de Bruxelles