title: Thyroid hormone resistance and pituitary enlargement after thyroid ablation in a woman on levothyroxine treatment.
abstract: We report a patient with inappropriate secretion of thyrotropin (TSH) and a pituitary mass. Although she had been treated for biochemical hyperthyroidism with thyroid surgery and radioiodine ablation, she had never complained of specific symptoms or demonstrated signs of overt thyroid dysfunction. On evaluation, she had increased free thyroxine and TSH levels, normal serum glycoprotein alpha-subunit levels, and a significant TSH over-response to exogenous thyrotropin-releasing hormone stimulation. Magnetic resonance imaging with gadolinium enhancement showed a pituitary enlargement with suprasellar extension. An indium In 111 pentetreotide scan showed an abnormal focus of radionuclide accumulation in the pituitary area. Sequencing of the TRbeta gene showed that the patient was heterozygous for a new single nucleotide substitution resulting in the replacement of the normal arginine with a serine at amino acid 320 (R320S). We review the difficulties encountered in establishing a correct diagnosis in patients with inappropriate secretion of TSH in combination with pituitary enlargement. Due to its possible false-negative results, we do not recommend the use of indium In 111 pentetreotide as a tool in the differential diagnosis of inappropriate secretion of TSH.
authors.affiliation: Endocrinology Department, Servicio de Endocrinología, Hospital de la Princesa, Universidad Autónoma, Madrid, Spain. mmarazuela.hlpr@madrid.salud.org
authors.forename: Monica
authors.initials: M
authors.lastname: Marazuela
authors.forename: Lia
authors.initials: L
authors.lastname: Nattero
authors.forename: Dolores
authors.initials: D
authors.lastname: Moure
authors.forename: Iluminada
authors.initials: I
authors.lastname: García-Polo
authors.forename: Nicte
authors.initials: N
authors.lastname: Figueroa-Vega
authors.forename: Carlos
authors.initials: C
authors.lastname: Guijarro
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019943:Amino Acid Substitution; D003131:Combined Modality Therapy; D000075202:Contraindications; D004351:Drug Resistance; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D006964:Hyperpituitarism / Q000175:diagnosis* / Q000473:pathology; D006980:Hyperthyroidism / Q000532:radiotherapy / Q000628:therapy*; D008875:Middle Aged; D010902:Pituitary Gland / Q000473:pathology; D013004:Somatostatin / Q000031:analogs & derivatives*; D037042:Thyroid Hormone Receptors beta / Q000235:genetics; D013974:Thyroxine / Q000627:therapeutic use*
chemical_list: D037042:Thyroid Hormone Receptors beta; D013004:Somatostatin; C081788:pentetreotide; D013974:Thyroxine