Foppiani Luca, Ruelle Antonio, Cavazzani Paolo, Del Monte Patrizia
Department of Endocrinology, Galliera Hospital, Mura Delle Cappuccine 14, 16128 Genova, Italy.
Cases J. 2009 Jul 29;2:6449. doi: 10.4076/1757-1626-2-6449.
Measuring thyroid stimulating hormone levels alone may be insufficient to appropriately evaluate thyroid function. Reduced thyroid stimulating hormone levels associated to normal/reduced FT4 levels should prompt investigation of pituitary function, on suspicion of hypopituitarism. Pituitary macroadenomas are the most common cause of hypopituitarism; among these, macroprolactinomas are usually treated with dopamine-agonist therapy. Hypopituitarism does not preclude the development of primary hyperthyroidism. This report describes the case of a patient with a final diagnosis of macroprolactinoma inducing hypopituitarism, who subsequently developed hyperthyroidism due to a toxic thyroid nodule.
A 62-year-old man underwent biochemistry and thyroid function assessment for asthenia. Reduced thyroid stimulating hormone levels were associated to slightly decreased FT4 levels and low-normal FT3 levels; thyroid ultrasonography showed a multinodular goiter. Thyroid scan with (99m)Tc-pertechnetate revealed an autonomous left nodule with suppression of the surrounding parenchyma. Pituitary investigation showed partial hypopituitarism associated to increased prolactin levels: 182-200 ng/ml. Magnetic resonance imaging revealed a large (2.2 cm) invasive macroadenoma. To avoid a possible high-dose hook effect, the patient's serum was diluted; the resulting PRL levels of around 1800 ng/ml prompted the final diagnosis of macroprolactinoma. Reduced libido and erectile dysfunction were ascertained. In addition to replacement therapy with L-thyroxine and testosterone, cabergoline was started and was progressively increased to high doses (4 g/week); this yielded a significant but incomplete reduction of PRL levels (63-99 ng/ml). Sexual function improved. The macroadenoma shrank over the first two years of therapy, but subsequently enlarged slightly. Following stereotactic radiosurgery, the tumor stabilized and prolactin almost normalized (22 ng/ml) on therapy. Over the years, thyroid nodule volume was unmodified, but hyperthyroidism on L-thyroxine therapy was found, and increased FT3 levels with suppressed thyroid stimulating hormone levels were confirmed off-therapy. Thyroid scan confirmed the left autonomous nodule, which was successfully treated with methimazole.
Reduced thyroid stimulating hormone levels associated to normal/reduced free-thyroid hormone levels may be the first clue to unsuspected hypopituitarism. Moderately increased prolactin levels in the presence of a large macroadenoma warrant serum dilution in order to avoid a possible hook effect. Stereotactic radiosurgery is a useful non-invasive tool in the management of pituitary tumors. A pre-toxic thyroid nodule with low secretory activity may initially be masked by the coexistence of secondary hypothyroidism, but may lead to overt hyperthyroidism over time.
仅检测促甲状腺激素水平可能不足以准确评估甲状腺功能。促甲状腺激素水平降低且游离甲状腺素（FT4）水平正常或降低时，应怀疑垂体功能减退并进行相关检查。垂体大腺瘤是垂体功能减退最常见的原因；其中，大泌乳素瘤通常采用多巴胺激动剂治疗。垂体功能减退并不排除原发性甲状腺功能亢进的发生。本报告描述了一例最终诊断为大泌乳素瘤导致垂体功能减退的患者，该患者随后因毒性甲状腺结节而发生甲状腺功能亢进。
一名62岁男性因乏力接受生化及甲状腺功能评估。促甲状腺激素水平降低，同时FT4水平略有下降，FT3水平处于低正常范围；甲状腺超声显示为结节性甲状腺肿。用高锝酸盐（99mTc）进行甲状腺扫描显示左叶有一个自主性结节，周围实质受抑制。垂体检查显示部分垂体功能减退，泌乳素水平升高：182 - 200 ng/ml。磁共振成像显示一个大的（2.2 cm）侵袭性大腺瘤。为避免可能的高剂量钩状效应，对患者血清进行了稀释；稀释后泌乳素水平约为1800 ng/ml，最终诊断为大泌乳素瘤。已确定存在性欲减退和勃起功能障碍。除用左甲状腺素和睾酮进行替代治疗外，开始使用卡麦角林，并逐渐增加至高剂量（4 μg/周）；这使泌乳素水平有显著但不完全的降低（63 - 99 ng/ml）。性功能有所改善。在治疗的头两年大腺瘤缩小，但随后略有增大。立体定向放射外科治疗后，肿瘤稳定，治疗期间泌乳素几乎恢复正常（22 ng/ml）。多年来，甲状腺结节体积未变，但发现左甲状腺素治疗期间出现甲状腺功能亢进，停药后证实FT3水平升高且促甲状腺激素水平受抑制。甲状腺扫描证实了左叶自主性结节，用甲巯咪唑成功治疗。
促甲状腺激素水平降低且游离甲状腺激素水平正常或降低可能是未被怀疑的垂体功能减退的首要线索。存在大腺瘤且泌乳素水平中度升高时，应进行血清稀释以避免可能的钩状效应。立体定向放射外科是垂体肿瘤治疗中一种有用的非侵入性工具。分泌活性低的毒性甲状腺结节最初可能因继发性甲状腺功能减退的并存而被掩盖，但随着时间推移可能导致明显的甲状腺功能亢进。
