Yap Yew Wen, Ball Steve, Qureshi Zubair
Leighton Hospital, Crewe, Crewe, UK
Manchester University NHS Foundation Trust, Manchester, UK
Endocrinol Diabetes Metab Case Rep. 2018 Sep 25;2018:18-0083. doi: 10.1530/EDM-18-0083.
The coexistence of primary hypothyroidism and thyroid-stimulating hormone (TSH)-stimulating pituitary macroadenoma can be a rare occurrence and can make diagnosis very challenging. We describe a case of a 44-year-old female with a history of fatigue, poor concentration, weight gain and amenorrhoea together with biochemical evidence of primary autoimmune hypothyroidism. Her initial TSH levels were elevated with low normal free thyroxine (T4) levels. Levothyroxine treatment was initiated and the dose was gradually titrated to supraphysiologic doses. This led to the normalisation of her TSH levels but her free T4 and triiodothyronine (T3) levels remained persistently elevated. This prompted a serum prolactin check which returned elevated at 2495 μ/L, leading onto pituitary imaging. A MRI of the pituitary gland revealed a pituitary macroadenoma measuring 2.4 × 2 × 1.6 cm. Despite starting her on cabergoline therapy with a reduction in her prolactin levels, her TSH levels began to rise even further. Additional thyroid assays revealed that she had an abnormally elevated alpha subunit at 3.95 (age-related reference range <3.00). This corresponded to a thyroid-secreting hormone pituitary macroadenoma. She went on to have a transphenoidal hypophysectomy. Histology revealed tissues staining for TSH, confirming this to be a TSH-secreting pituitary macroadenoma. This case highlighted the importance of further investigations with thyroid assay interferences, heterophile antibodies, alpha subunit testing and anterior pituitary profile in cases of resistant and non-resolving primary hypothyroidism. Learning points: •• Levothyroxine treatment in primary hypothyroidism can potentially unmask the presence of a latent TSH-secreting pituitary macroadenoma, which can make diagnosis very challenging. •• A high index of suspicion should prompt clinicians to further investigate cases of primary hypothyroidism which despite increasing doses of levothyroxine treatment with normalisation of TSH, the free T4 and T3 levels remain persistently elevated. •• Clinicians should consider investigating for adherence to levothyroxine, thyroid assay interference, heterophile antibodies, TSH dilution studies, alpha subunit and anterior pituitary profile testing to further clarity the diagnosis in these patients. •• Although coexistent cases of TSHoma with primary hypothyroidism are rare, it should always be in the list of differential diagnoses in cases of unresolving primary hypothyroidism.
原发性甲状腺功能减退症与促甲状腺激素（TSH）分泌性垂体大腺瘤并存的情况较为罕见，诊断极具挑战性。我们报告一例44岁女性，有疲劳、注意力不集中、体重增加和闭经病史，同时有原发性自身免疫性甲状腺功能减退症的生化证据。她最初的TSH水平升高，游离甲状腺素（T4）水平略低于正常下限。开始给予左甲状腺素治疗，并逐渐滴定至超生理剂量。这使她的TSH水平恢复正常，但游离T4和三碘甲状腺原氨酸（T3）水平仍持续升高。这促使进行血清催乳素检查，结果显示升高至2495 μ/L，随后进行垂体成像检查。垂体磁共振成像（MRI）显示一个大小为2.4×2×1.6 cm的垂体大腺瘤。尽管开始使用卡麦角林治疗使催乳素水平降低，但她的TSH水平开始进一步升高。进一步的甲状腺检查显示，她的α亚基异常升高至3.95（年龄相关参考范围<3.00）。这符合分泌甲状腺激素的垂体大腺瘤。她随后接受了经蝶窦垂体切除术。组织学检查显示组织TSH染色阳性，证实这是一个分泌TSH的垂体大腺瘤。该病例强调了在原发性甲状腺功能减退症耐药且病情未缓解的情况下，通过甲状腺功能检查干扰因素、嗜异性抗体、α亚基检测和垂体前叶激素谱进一步检查的重要性。学习要点：••原发性甲状腺功能减退症的左甲状腺素治疗可能会潜在地揭示隐匿性分泌TSH的垂体大腺瘤的存在，这会使诊断极具挑战性。••高度怀疑应促使临床医生对原发性甲状腺功能减退症患者进行进一步检查，尽管左甲状腺素治疗剂量增加且TSH恢复正常，但游离T4和T3水平仍持续升高。••临床医生应考虑调查左甲状腺素的依从性、甲状腺功能检查干扰因素、嗜异性抗体、TSH稀释研究、α亚基和垂体前叶激素谱检测，以进一步明确这些患者的诊断。••尽管TSH瘤与原发性甲状腺功能减退症并存的情况罕见，但在原发性甲状腺功能减退症病情未缓解的病例中，它应始终在鉴别诊断列表中。
