Effects of Thyroid Hormones (T4, T3), Bromocriptine and Triac on Inappropriate TSH Hypersecretion

Abstract

Inappropriate TSH hypersecretion was diagnosed in a 38-year-old woman (case 1) and in a 38-year-old man (case 2). Both of them had earlier been treated by ablative therapy for hyperthyroidism. The present diagnosis was based on elevated basal serum TSH levels despite elevated serum free thyroid hormone levels. Both of them had exaggerated TSH responses to TRH (peak value 240 mU/l in case 1 and 408 mU/l in case 2). Their albumin and prealbumin levels were normal. The serum TBG level was normal in case 1 but was elevated in case 2. Serum levels of alpha-subunits of TSH, and pituitary CT scans were normal. Despite mild clinical hyperthyroidism, peripheral indices of thyroid hormone action were normal. They had also relatives with apparent resistance to thyroid hormones. In view of the possibility that prolonged pituitary thyrotrophic stimulation is detrimental, various therapeutic approaches to suppress TSH levels were tried. Both T3 and T4 treatments lowered serum TSH levels, but were poorly tolerated. Acute administration of L-dopa or bromocriptine reduced serum TSH levels, but this was not seen during long-term therapy. TRIAC treatment lowered serum TSH levels, and the drug was well tolerated. Serum TSH responses to TRH were not blunted during T3, T4 or TRIAC treatments. Somatostatin also reduced serum TSH levels, but did not potentiate the effect of low dose T3 therapy. Our results suggest that the patients had unbalanced pituitary and peripheral thyroid hormone resistance, predominantly at the pituitary level. Of the drugs studied, TRIAC seemed to be the most suitable therapy.

Triiodothyroacetic acid in health and disease

“…In a subgroup of RTHβ patients, TA 3 is able to decrease TSH and consequently the high serum T 4 and T 3 levels. Since the thyromimetic effects of TA 3 itself do not fully compensate the reduction in endogenous TH levels, it alleviates the thyrotoxic symptoms including tachycardia, goiter, excessive sweating and behavioral problems (BeckPeccoz et al 1983, Lind & Eber 1986, Faglia et al 1987, Salmela et al 1988, Kunitake et al 1989, Smallridge et al 1989, Beck-Peccoz et al 1990, Aguilar Diosdado et al 1991 Crino et al 1992, Dulgeroff et al 1992, Ueda et al 1996, Darendeliler & Basx 1997, Radetti et al 1997, CliftonBligh et al 1998, Persani et al 1998, Asteria et al 1999, Kong et al 2005, Torre et al 2005, Wu et al 2006, Gurgel et al 2008, Santos et al 2008, Guran et al 2009, Anzai et al 2012, Ferrara et al 2012, Ramos-Prol et al 2013, Stagi et al 2014, Chatzitomaris et al 2015, Xue et al 2015. However, some patients do not respond to TA 3 treatment, which is assumed to depend on the type or location of the mutation (Hamon et al 1988, Persani et al 1998.…”

Eficacia de la quinagolida en el tratamiento de un paciente con resistencia hipofisaria a hormonas tiroideas

“…La triyodotironina se ha demostrado efectiva, aunque su efecto es limitado debido a su corta vida media (6,10). La Dtiroxina también consigue suprimir la TSH y mejora los sínto-mas y signos de hipertiroidismo en los pacientes con RHHT (7), aunque aún es necesario confirmar su efectividad a largo plazo.…”

Imaging of dopamine D2 and somatostatin receptors in vivo using single-photon emission tomography in a patient with a TSH/PRL-producing pituitary macroadenoma

“…However, in three patients with inappropriate TSH secretion but without a proven pituitary adenoma, TRIAC was the most suitable therapy for diminishing the TSH secretion [3,33]. Therefore, these two disorders may respond differently to TRIAC.…”