Thyrotoxicosis and Pregnancy


Question

Dear Sir- What one would do with a 20 years old lady with a recently diagnosed graves disease who would like to get married next week. Her partner refused to delay the wedding and will not accept her to be on contraception. What would be the optimum management. Should we operate on her. Would it be better to do total or subtotal thyroidectomy. Is thyroid replacement therapy safe in pregnancy.

Dr Tarek Elatrozy, Gharbia, Egypt

Response

Thyroid replacement is certainly perfectly safe in pregancy. I hesitate to say what is optimum management, not knowing all about the patient. However it is common to carry patients thru pregnancy on antithyroid drugs, with caution not to overdose the antithyroid drug. If there is difficulty with medical management, it is also considered safe to prepare the patient with antithyroid drugs, and operate in the mid trimester. Usually the operation is a subtotal thyroidectomy, but some people prefer a more complete thyroidectomy if the surgeon is skilled and has a low risk of parathyroid or nerve damage in practice. Does this provide what you need?

L De Groot,MD

Hypothyroidism, Renal Insufficiency, and RAI Therapy


Question

I am a physician with a 3.5 cm papillary thyroid cancer 5.5 weeks post total-thyroidectomy (no macroscopic extension, no known distant mets, but a few positive lymph nodes) about to undergo ablation with 150 mCi iodine next week. I was otherwise healthy, 43 years old, with no meds and no prior medical problems. Post operative calcium has been low 8.7 (reference 8.9-10.3), PTH - 48 (reference 14-72) - 48 hours off of calcium supplements. My concern is that my creatinine has crept up from 1.2 to 1.7 over the past two weeks as my TSH has risen above 65 - with BUN 5 to 8, C02 31 and otherwise normal electrolytes, normal albumin, total protein. I have read a few small series about renal insufficiency with profound hypothyroidism induced decreases in GFR [Kreisman SH. Arch Intern Med 1999; 159: 79-82]. A few related questions. What is your experience with this phenomenon - if any? Is it fully reversible? Is there anything I can do to ameliorate this decline and the potential for long term renal injury? Does my dose of radioactive iodine need to be cut due to renal insufficiency?

S Rothrock MD, Orlando, Florida

First Response

Dear Colleague, The decrease in glomerular filtration rate in severe acute hypothyroidism is a well known phenomenon . This abnormality is in principle completely reversible. The most recent study on this problem that I know is pasted below. Theoretically it is possible that clearance of radio-active iodine is diminished as well, if clearance is through glomerular filtration and not via tubular function which seems to be untouched in hypothyroidism( see below). I have no recent information on the mechanism of renal excretion of iodide. However, I assume that the doses given for ablation to patients with elevated TSH due to hypothyroidism (and not after administration of recombinant human TSH) are mostly if not always when creatinine clearance is decreased. In other words these doses are apparently chosen under conditions of decreased glomerular filtration. I think therefore that there is no reason in your case for any correction of the dose. Furthermore different departments administer different doses of radio-active iodine for thyroid ablation, varying between 30 and 100 mCi. These variations are probably much more substantial than the variations in glomerular filtration rate. Last but not least I am not aware of any potential damage to healthy kidneys after ablative doses of radioactive iodine.I invite Dr DeGroot to add his comments to your question as well.

Georg Hennemann, MD

Second Response

The answers to your questions are a bit complicated You should also consult with a nephrologist to be sure there is no underlying renal disease.. However, my thoughts are as follows. Definitely severe hypothyroidism can reduce GFR and increase Cr, and this should be fully reversible. I am surprised that the BUN is so low, but perhaps this is also due to a decrease in diet and decreased metabolism . Generally a TSH above 30 is considered adequate for treatment. Severe hypothyroidism can be avoided by using the "Half dose protocol" , or recombinant TSH, as described in THYROIDMANAGER. There are wide variations in the dose chosen for ablation, with reasons for most choices. Your dose is on the "highish" side , I believe. The whole body radiation exposure will be increased by hypothyroidism and diminished GFR. Generally the whole body radiation is reasonably low in this proceedure, but can only be determined by knowing the dose administered, thyroid uptake, and retention time. It often is about 1/3 to 1/2 rad per mCi given, but this is only true if there is little RAIU in the thyroid. A nuclear medical person could give more accurate figures when RAIU is known. Renal insufficiency would increase whole body radiation to some extent, but its effect on treatment of the residual thyroid would not necessarily be in the same direction since retention of stable iodine might tend to decrease fractional RAIU. Your nuclear medical therapist is really in the best position to answer these questions, which involve several factors that are not available to me. In general keeping well hydrated would help reduce 131-I retention in the body, but perhaps this should also be done with caution, since there is a recent report of severe hyponatremia occurring in this situation. I hope these rather scattered comments are of use.

L De Groot,MD

Surgery With Adrenal Mass; “Incidental” Medullary Carcinoma


Question

Thank you so much for responding to my e mails. I wish to get your views on these cases. 1) 43 year old male diagnosed with NHLymphoma 1991,post surgery,post RT.Incidental finding of 1.3 cm adrenal adenoma right, serial ct/mri of the adrenals showed increase in size 2003 1.8 cm,2004 1.6 cm. He is clinically ok, non hypertensive, the nodule looks silent and benign, HU <10. My questions are: a) he is to undergo a nasal surgery under general anesthesia, is it safe to proceed with surgery or do we have to r/o functioning adrenal nodule first? b) he also has subclinical hypothyroidism,ft4 11,tsh 12,anti tg>2000,anti tpo 130,thyroid scan, hyperfunctioning and warm nodules. Can his subhypo be attributed to the radiation he received while during treatment for HL ymphoma of the axillary node or is this definitely thyroiditis alone? can we also consider the thyroid nodules to be radiation exposure related? 2) female late 20s, 2002 presented with subclinical hypothyroidism and a discreet solid nodule on the right lobe.FNAC was colloid nodule. She received t4 suppression for about a year before finally deciding to have thyroidectomy. NO FROZEN section, surgery done at the suburb. Histopath showed medullary ca. Problem: surgery done was subtotal. Parathyroids were normal looking says the surgeon, patient non hypertensive .Should we subject patient to completion thyroidectomy, can we be guided by calcitonin level and cea alone at this time. 3) What exactly is the clinical significance of (histopath reading) HYPERPLASTIC nodules.We see a lot of these lately. Thanks so much sir for your time and wisdom.

Lynn F.W.Bilar,MD

Response

  1. The adrenal mass seems to be a non functioning incidentaloma. The only test that I would recommend in view of a general anasthesia is measurement of plasma/urinary epinephrins just to exclude the rare possibility of pheocromocytoma. Regarding the thyroid, definitely the patient has autoimmune thyroiditis with subclinical hypothyroidism. This can develop spontaneously on a genetic background but that are also convincing evidence that autoimmune thyroiditis may be triggered by exposure to external radiation. Clinically it makes no difference, except that true cold nodules in the setting of radiation exposure have higher chance to be malignant and thus must be submitted to FNAC.
  2. Medullary thyroid cancer is a potentially lethal disease and frequently presents with lymph node metastases, either clinically evident or unsuspected. In my opinion the patient should undergo a careful ultrasound of the neck for lymph nodes and calcitonin measurements before and after pentagastrin stimulation. If the results are fine, I would procede with completion thyroidectomy and dissection of the central node compartment. If there is suspicion of lateral lymph node involvement surgery should be more aggressive. In addition, being the patient young one should screen blood DNA for germline mutations of the ret proto-oncogene. This is because about 5-7% of apparently sporadic MTCs are indeed hereditary cases or "de novo" disease misdiagnosed as sporadic.
  3. In my view hyperplastic nodule should refer to nodules as those found in the context of goiter where the disease is expression of minor TSH hyperstimulation, These leions are usually policlonal in origin as opposed to true adenomas which are usually monoclonal proliferations. I hope that this information answers your questions.

Sincerely,

Furio. Pacini MD