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 Table of Contents  
Year : 2020  |  Volume : 17  |  Issue : 2  |  Page : 86-88

Intrathyroidal parathyroid adenoma: A perplexing entity

1 Department of Colorectal Surgery, Bedford NHS Trust, Bedford, UK
2 Department of Endocrinology and Diabetes, Maharaja Agrasen Hospital, New Delhi, India
3 Department of Endocrine Surgery, Maharaja Agrasen Hospital, New Delhi, India
4 Department of Nuclear Medicine, All India Institute of Medical Sciences (AIIMS), New Delhi, India
5 Department of Radiology, Maharaja Agrasen Hospital, New Delhi, India

Date of Submission25-Mar-2020
Date of Acceptance27-Mar-2020
Date of Web Publication17-Jul-2020

Correspondence Address:
Dr. Deepak Khandelwal
Department of Endocrinology and Diabetes, Maharaja Agrasen Hospital, Punjabi Bagh, New Delhi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/trp.trp_18_20

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Intrathyroidal parathyroid adenoma (IPA) can be a cause of failed cervical exploration for primary hyperparathyroidism (PHPT). There is a lot of controversy regarding the correct approach and extent of exploration in such cases. Herein, we report the case of a 37-year-old female who was managed for PHPT with right-sided IPA after correlating preoperative ultrasonography and99mTc-sestamibi scan. A high index of suspicion, preoperative identification, and planning is very important to avoid unnecessary dissection and failure to remove the diseased gland in such cases.

Keywords: Intrathyroidal parathyroid adenoma, parathyroid exploration, primary hyperparathyroidism, thyroid nodule

How to cite this article:
Gupta M, Khandelwal D, Aggarwal V, Damle NA, Garg M. Intrathyroidal parathyroid adenoma: A perplexing entity. Thyroid Res Pract 2020;17:86-8

How to cite this URL:
Gupta M, Khandelwal D, Aggarwal V, Damle NA, Garg M. Intrathyroidal parathyroid adenoma: A perplexing entity. Thyroid Res Pract [serial online] 2020 [cited 2022 Sep 25];17:86-8. Available from: https://www.thetrp.net/text.asp?2020/17/2/86/289996

  Introduction Top

Although uncommon, an intrathyroidal parathyroid adenoma (IPA) can be an important cause of surgical failure in patients with primary hyperparathyroidism (PHPT).[1] First described by Lahey in the year 1926, an intrathyroidal parathyroid gland (true intrathyroidal parathyroid gland) is a normal or abnormal parathyroid gland, situated totally within the thyroid, surrounded on all aspects by thyroid parenchyma and with no capsule.[2] This entity must be clearly distinguished from the subcapsular/intracapsular parathyroid gland and those glands located in crevices in the thyroid. There is a lot of controversy regarding the correct approach and extent of exploration in cases where an IPA is suspected. The extent ranges from carrying out a bilateral neck exploration along with thymus exploration, to undertaking a partial or complete thyroid lobectomy and even thyroidectomy and enucleation.[3],[4],[5] Herein, we report a case of PHPT resulting from IPA managed at our center.

  Case Report Top

A 37-year-old woman presented for the evaluation of recurrent renal stones for the last 5 years. On investigations, she was detected to have hypercalcemia (multiple reports ranging between 12 and 14 mg/dl; normal range 8.8–10.8 mg/dl). She denied any bony symptoms, dyspepsia, or proximal muscle weakness. There was no palpable abnormal mass/nodule in the region of the neck. Her intact parathyroid hormone (iPTH) level was 245 pg/ml (normal 15–65 pg/ml), and 25(OH) vitamin D was 31 ng/ml (normal range 30–100 ng/ml). Her thyroid function test was within normal limits. A presumptive biochemical diagnosis of PHPT was made, and she underwent ultrasonography (USG) of the neck for localization of parathyroid adenoma, which revealed a solid hypoechoic lesion of 1.5 cm × 1.5 cm located within the right lobe of the thyroid inferiorly [Figure 1]. No other enlarged/abnormal parathyroid glands could be seen.99m Tc-sestamibi scan was done which revealed an abnormal enhanced uptake in the region of the inferior part of the right lobe of the thyroid [Figure 2]. After correlating the USG report along with the abnormal uptake in the sestamibi scan, a diagnosis of intrathyroid parathyroid adenoma was considered. After detailed discussion and consent with the patient and family, decision was taken for exploration with a possibility of right thyroid lobectomy.
Figure 1:Ultrasound neck showing abnormal hypoechoic lesion within the right lobe of the thyroid

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Figure 2: Early and delayed 99mTc-sestamibi scan images. Physiological uptake is seen in the thyroid, salivary glands, myocardium, and liver with thyroidal tracer washout in the delayed images. Large focus of abnormally increased tracer uptake is seen in the region of the lower pole of the right lobe of the thyroid, in both early and delayed images – consistent with a parathyroid adenoma

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The right lower parathyroid gland could not be found anywhere even after detailed exploration including exploration of the thyrothymic ligament. The right lobe of the thyroid was removed based on preoperative imaging after safeguarding the right superior parathyroid gland which appeared normal on inspection. The right thyroid lobe was cut open ex vivo in order to avoid spillage. A large 1.6 cm × 1.5 cm × 1.3 cm, oval-shaped lesion completely encased within the thyroid gland was found correlating with the USG and sestamibi scan, and this was confirmed using frozen section [Figure 3]. We opted not to explore the other side of the thymus in order to avoid unnecessary dissection. Serum iPTH and calcium levels became normal postoperatively.
Figure 3: Gross specimen of parathyroid adenoma dissected from within the thyroid gland

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  Discussion Top

IPAs are the second most common cause of persistent hyperparathyroidism, after intrathymic adenomas.[6] True IPA occurred in only 0.7% of 10,000 primary cases, whereas another 1.2% were closely adherent to or partially within the thyroid substance.[7] IPA occurs in predictable locations within the thyroid gland, with the vast majority occurring in the lower lateral quadrant and a small percentage near the recurrent nerve and superior pole.[4],[7] The parathyroid gland occurs as an intrathyroidal variety when it becomes trapped within the thyroid as the lateral and medial lobes fuse. Although this is the common mechanism for both superior and inferior glands, the latter (derived from the 3rd branchial pouch) are pulled by the thymus during its descent, and because of migrating a longer distance, they have an increased chance of becoming entrapped during the fusion of the thyroid lobes.[8] Most useful investigations in the localization of IPA are USG and99m Tc-sestamibi scans.[9] According to a case series consisting of 53 patients with intrathyroidal parathyroid, sestamibi and USG correctly identified the adenoma in 35 (70%) and 11 (61%) cases, respectively.[10]

In USG, the main diagnostic difficulty lies in distinguishing IPA from thyroid nodules. The proposed USG criteria for identifying a parathyroid adenoma include solid composition, profound hypoechogenicity, and presence of a feeding polar vessel.[11],[12],[13] In a retrospective review, the sensitivity and specificity for differentiating an IPA from a thyroid nodule were 78% and 86%, respectively.[14] In sestamibi scan, likely error in diagnosis is because of errors in interpretation rather than errors in the scan itself.[15] Newer imaging modalities such as18 F-choline photon emission tomography/computed tomography can be very helpful in such cases, although this was not done in our case.[16]

Exhaustive literature review fails to provide enough evidence of a set protocol/extent of surgery for suspected IPA in general.[1],[4],[17] Goodman et al. believed that lobectomies are often performed indiscriminately in search of a missing parathyroid and are typically unsuccessful. As per their group, the missing gland can be found by careful dissection of the loose tissue surrounding the thyroid, thyroidectomy, or meticulous exploration of the lateral inferior lobe.[4] In our case, we opted for right thyroid lobectomy rather than indulging in thyroidectomy and enucleation based on other experiences to minimize the possibility of overlooking an IPA and avoid spillage (rupture of the capsule and parathyromatosis).[5],[17]

  Conclusion Top

The clinical pearls in a case of IPA are summarized in [Table 1]. IPA should be considered an important cause of PHPT. USG performed by an experienced sonologist and a correctly interpreted99m Tc-sestamibi scan are useful adjuncts to identify IPA preoperatively. Exhaustive literature review fails to provide enough evidence of a set protocol/extent of surgery for suspected IPA in general. However, preoperative identification and planning is of utmost importance to avoid unnecessary dissection. Thymectomy and bilateral neck exploration is not always necessary. Approach for every case should be individualized.
Table 1: Clinical pearls in the diagnosis and management of intrathyroidal parathyroid adenoma

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Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initial will not be published, and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Wang C. Hyperfunctioning intrathyroid parathyroid gland: A potential cause of failure in parathyroid surgery. J R Soc Med 1981;74:49-52.  Back to cited text no. 1
Wang C. The anatomic basis of parathyroid surgery. Ann Surg 1976;183:271-5.  Back to cited text no. 2
Davis O, Scanlon EF, Pollak ER, Casey JJ, Victor TA. Bilateral intrathyroidal hyperplastic parathyroid glands. J Surg Oncol 1984;27:271-4.  Back to cited text no. 3
Goodman A, Politz D, Lopez J, Norman J. Intrathyroid parathyroid adenoma: Incidence and location—the case against thyroid lobectomy. Otolaryngol Head Neck Surg 2011;144:867-71.  Back to cited text no. 4
Ros S, Sitges-Serra A, Pereira JA, Jimeno J, Prieto R, Sancho JJ, et al. Intrathyroid parathyroid adenomas: Right and lower. Cir Esp 2008;84:196-200.  Back to cited text no. 5
Wheeler MH, Williams ED, Wade JS. The hyperfunctioning intrathyroidal parathyroid gland: A potential pitfall in parathyroid surgery. World J Surg 1987;11:110-4.  Back to cited text no. 6
Low RA, Katz AD. Parathyroidectomy via bilateral cervical exploration: A retrospective review of 866 cases. Head Neck 1998;20:583-7.  Back to cited text no. 7
Feliciano DV. Parathyroid pathology in an intrathyroidal position. Am J Surg 1992;164:496-500.  Back to cited text no. 8
Abboud B, Sleilaty G, Ayoub S, Hachem K, Smayra T, Ghorra C, et al. Intrathyroid parathyroid adenoma in primary hyperparathyroidism: Can it be predicted preoperatively? World J Surg 2007;31:817-23.  Back to cited text no. 9
Mazeh H, Kouniavsky G, Schneider DF, Makris KI, Sippel RS, Dackiw AP, et al. Intrathyroidal parathyroid glands: Small, but mighty (a Napoleon phenomenon). Surgery 2012;152:1193-200.  Back to cited text no. 10
Chen J, Ma Z, Yu J. Diagnostic pitfalls in a cystic ectopic intrathyroidal parathyroid adenoma mimicking a nodular goiter: A care-compliant case report. Medicine (Baltimore) 2019;98:e14351.  Back to cited text no. 11
Ye T, Huang X, Xia Y, Ma L, Wang L, Lai X, et al. Usefulness of preoperative ultrasonographic localization for diagnosis of a rare disease: Intrathyroid parathyroid lesions. Medicine (Baltimore) 2018;97:e10999.  Back to cited text no. 12
Yabuta T, Tsushima Y, Masuoka H, Tomoda C, Fukushima M, Kihara M, et al. Ultrasonographic features of intrathyroidal parathyroid adenoma causing primary hyperparathyroidism. Endocr J 2011;58:989-94.  Back to cited text no. 13
Heller MT, Yip L, Tublin ME. Sonography of intrathyroid parathyroid adenomas: Are there distinctive features that allow for preoperative identification? Eur J Radiol 2013;82:e22-7.  Back to cited text no. 14
Sadacharan D, Mahadevan S, Ravikumar K, Muthukumar S. An interesting case of intrathyroidal parathyroid adenoma. BMJ Case Rep. 2015;2015:bcr2015210351. Published 2015 May 6. doi:10.1136/bcr-2015-210351.  Back to cited text no. 15
Prabhu M, Kumari G, Damle NA, Arora G, Kumar P, Kumar R, et al. Assessment of the role of early dynamic PET/CT with 18F-fluorocholine in detection of parathyroid lesions in patients with primary hyperparathyroidism. Nucl Med Commun 2018;39:1190-6.  Back to cited text no. 16
Ryan S, Courtney D, Moriariu J, Timon C. Surgical management of primary hyperparathyroidism. Eur Arch Otorhinolaryngol 2017;274:4225-32.  Back to cited text no. 17


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1]

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