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Open access

Yew Wen Yap, Steve Ball and Zubair Qureshi

Summary

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.
Open access

Ana G Ferreira, Tiago N Silva, Henrique V Luiz, Filipa D Campos, Maria C Cordeiro and Jorge R Portugal

Sellar plasmacytomas are rare and the differential diagnosis with non-functioning pituitary adenomas might be difficult because of clinical and radiological resemblance. They usually present with neurological signs and intact anterior pituitary function. Some may already have or eventually progress to multiple myeloma. We describe a case associated with extensive anterior pituitary involvement, which is a rare form of presentation. A 68-year-old man was referred to our Endocrinology outpatient clinic due to gynecomastia, reduced libido and sexual impotence. Physical examination, breast ultrasound and mammography confirmed bilateral gynecomastia. Blood tests revealed slight hyperprolactinemia, low testosterone levels, low cortisol levels and central hypothyroidism. Sellar MRI showed a heterogeneous sellar mass (56 × 60 × 61 mm), initially suspected as an invasive macroadenoma. After correcting the pituitary deficits with hydrocortisone and levothyroxine, the patient underwent transsphenoidal surgery. Histological examination revealed a plasmacytoma and multiple myeloma was ruled out. The patient was unsuccessfully treated with radiation therapy (no tumor shrinkage). Myeloma ultimately developed, with several other similar lesions in different locations. The patient was started on chemotherapy, had a bone marrow transplant and is now stable (progression free) on lenalidomide and dexamethasone. The presenting symptoms and panhypopituitarism persisted, requiring chronic replacement treatment with levothyroxine, hydrocortisone and testosterone.

Learning points:

  • Plasmacytomas, although rare, are a possible type of sellar masses, which have a completely different treatment approach, so it is important to make the correct diagnosis.
  • Usually, they present with neurological signs and symptoms and a well-preserved pituitary function, but our case shows that anterior pituitary function can be severely compromised.
  • Making a more extensive evaluation (clinical and biochemical) might provide some clues to this diagnosis.