NMS Q&A Family Medicine

Thyroid Diseases 20710. The answer is A. Papillary thyroid carcinoma is theleast aggressive and happily the most common, comprising76% of all thyroid cancers. Follicular thyroid carcinomais the most well differentiated of the thyroid cancers;the second most well differentiated is papillary carcinoma.Medullary carcinoma of the thyroid occurs equally frequentlyin male and female individuals, whereas anaplasticcarcinoma occurs 56% of the time in female individuals.Follicular carcinoma constitutes 16% of all thyroid carcinomas.Because of good differentiation, follicular carcinomais also amenable to I 131 therapy after totalthyroidectomy. To a lesser degree, this applies to papillarycarcinoma as well. Patients with medullary carcinomahave a 6% chance of dying of the disease; those with follicularcarcinoma have a 24% chance of dying of the disease.Although papillary carcinoma is the least aggressive,it tends to be multifocal and presents frequently withlymph node metastases. These, however, tend to respondto I 131 therapy.11. The answer is E. Contrary to popular lore, hypothyroidism,although rendering it more difficult to loseweight because of reduced basal requirements, does notcause true obesity. Along with reduced basal energyrequirements, the appetite appears to be reduced proportionately.Each of the other choices is well known to bepowerfully associated with hypothyroidism except foramenorrhea. Conventional wisdom as taught to medicalstudents is that thyrotoxicosis is associated with oligomenorrheaor amenorrhea, whereas hypothyroidism is associatedwith menorrhagia. Actually, either amenorrhea ormenorrhagia may be found in hypothyroidism. Thus, anyform of menstrual irregularities warrants routine thyroidfunction studies.12. The answer is D. “The patient has secondary hypothyroidism”is an incorrect statement. Secondary hypothyroidismoccurs as a result of failure of the pituitarygland, specifically, inadequate TSH production, and henceit manifests lower than normal TSH levels, not elevatedlevels. Each of the other choices results in elevated TSH inprimary hypothyroidism. Malabsorption of thyroid medicationcan occur because of concurrent administrationof binding substance, sprue or diarrhea of any kind, orbile acid-binding agents like cholestyramine. In someautoimmune conditions, false elevations of TSH mayoccur through interference with the laboratory assay.13. The answer is A. Suppressed TSH, elevated FT 4 , andan abnormally low I 123 uptake are typical of acute thyroiditis.However, for confirmation, thyroglobulin shouldbe checked and found to be elevated. Otherwise, the diagnosismay be hypermetabolism caused by exogenous thyroidhormone. Acute thyroiditis causes a release of thyroidhormone resulting in a suppression of TSH, all of whichoccurs in the absence of active production of hormone bythe parenchyma; thus, there is no increase and may be adecrease in I 123 uptake. Choice B, suppressed TSH, elevatedFT 4 , and increased I 123 uptake, is typical of primaryhyperthyroidism. If the increased uptake is diffuse, thepicture is that of classical Graves disease. A nodular I 123uptake scan result may be multiple in toxic multinodulargoiter or single in the case of a toxic adenoma. Choice C,elevated FT 4 and elevated TSH, assuming no spuriouscause of TSH elevation, can occur only in secondaryhyperthyroidism (i.e., increased production of pituitaryTSH). Choice D, suppressed TSH, normal FT 4 , and normalT 3 , is evidence of subclinical hyperthyroidism, treatedhyperthyroidism (perhaps dosed slightly above therapeutic),pregnancy, or rarely nonthyroid illness. Choice E,suppressed TSH, elevated FT 4 , indicates exogenous thyroidhormone, as may occur in Choice D.14. The answer is E. Serum antithyroglobulin, taken on ablood sample, if elevated, makes the diagnosis of Hashimotothyroiditis in 90% of Hashimoto and to lesser sensitivityin other thyroiditides 40% of Hashimoto manifestantithyroglobulin titers. Hashimoto thyroiditis is themost common thyroid disorder in the United States. RAIuptake with I 123 , in the subacute phase, as with all thyroiditides,will be very low as opposed to Graves disease ornormal. However, as the disease becomes chronic, ineuthyroid or hypothyroid patients, the RAI uptake tendsto be normal or elevated with an uneven distribution.FNA biopsy would be indicated if there was a singleprominent nodule. In the absence of thyrotoxicosis, T 3determination is not indicated and then only if TSH issuppressed and FT 4 is normal. Hashimoto thyroiditis(also called lymphocytic thyroiditis or, archaically, strumalymphomatosa) uncommonly causes a thyrotoxic phasebut often leads to hypothroidism, remitting then in 5%of cases.15. The answer is E. Subacute thyroiditis, accountingfor about 5% of clinical thyroid disease, is usually painfulbut may be silent, the latter understandably causing confusionwith Hashimoto thyroiditis. It is often associatedwith systemic symptoms of viral-like illness during theearly phase. It has also been called de Quervain thyroiditis.Graves disease causes exophthalmos in addition toother signs of hyperthyroidism and manifests anincreased RAI uptake. Riedel struma does not cause thyrotoxicosis.Hashimoto thyroiditis does not present witha tender gland and only rarely manifests hyperthyroidism.Ludwig angina is a streptococcal infection of thefloor of the mouth and descending inferiorly. Thoughanterior neck pain would be characteristic, hyperthyroidismwould not.