Treatment options for a patient experiencing pruritic rash associated with transdermal testosterone: a review of the literature.

A 22-year-old man with hypogonadotropic hypogonadism was receiving monthly intramuscular injections of testosterone replacement therapy. The patient refused to self-administer the injections because of discomfort, so the therapy was switched to testosterone patches. He experienced a pruritic, macular, erythematous rash underneath the reservoir area of two different transdermal formulations, which did not improve after pretreatment with topical corticosteroids. Eventually, he tolerated application of a testosterone gel and his serum testosterone levels returned to normal after 1 month of therapy. Commercially available and investigational testosterone products and therapeutic monitoring guidelines for androgen replacement are reviewed.

Exaggerated levothyroxine malabsorption due to calcium carbonate supplementation in gastrointestinal disorders.

OBJECTIVE: To describe a patient with primary hypothyroidism in whom ingestion of levothyroxine with calcium carbonate led to markedly elevated serum thyrotropin concentrations. CASE SUMMARY: A 61-year-old white woman with primary hypothyroidism, systemic lupus erythematosus, celiac disease, and history of Whipple resection for pancreatic cancer was euthyroid with levothyroxine 175-188 micrograms/d. After taking a high dose of calcium carbonate (1250 mg three times daily) with levothyroxine, she developed biochemical evidence of hypothyroidism (thyrotropin up to 41.4 mU/L) while remaining clinically euthyroid. Delaying calcium carbonate administration by four hours returned her serum thyrotropin to a borderline high concentration (5.7 mU/L) within a month. Serum concentrations of unbound and total thyroxine and triiodothyronine tended to decrease, but remained borderline low to normal while the patient concomitantly received levothyroxine and calcium carbonate. DISCUSSION: Concomitant administration of levothyroxine and calcium carbonate often results in levothyroxine malabsorption. While in most patients the clinical consequences of this interaction, even with prolonged exposure, are relatively small, overt hypothyrodism may develop in patients with preexisting malabsorption disorders. However, as the current case illustrates, the clinical manifestations of the initial levothyroxine deficit may not always be apparent and, of all usual laboratory thyroid function tests, only thyrotropin measurement will reliably uncover the exaggerated levothyroxine malabsorption. CONCLUSIONS: Decreased absorption of levothyroxine when given with calcium carbonate may be particularly pronounced in patients with preexisting malabsorption disorders. Once recognized, a change in drug administration schedule usually minimizes or eliminates this interaction.