Endocrine Abstracts

Indroduction: Central hypothyroidism is a rare cause of hypothyroidism, consequence of various disorders affecting pituitary (secondary) or hypothalamus (tertiary hypothyroidism). Difficulties in the diagnosis and management of patients are due to the nontypical clinical picture, frequent combination with impaired function of other pituitary hormones, difficulties in laboratory assessment in high TSH levels or low - normal T4 free levels. Diagnosis is based on a confirmed decrease in the level of free T4 with a low or normal level of TSH. The standard treatment for hypothyroidism of any etiology remains monotherapy with levothyroxine, which allows to restore the euthyroid state in most patients. The criterion for the effectiveness of therapy is to maintain the level of T4 free in the upper half of the reference norm interval.

Case report: 71 y/o male patient presented in our clinic with complaints of severe fatigue, decreased appetite, myalgia and weakness in April of 2023. In February of 2021 he was hospitalized in NYC, Brooklyn, with a diagnosis of pneumonia, antibiotic therapy was initiated. His medical history revealed pituitary microadenoma with apoplexy without proper functional status assessment. Patient demonstrated progressive weakness, low blood pressure, especially for the last month. He was evaluated by the cardiologist and referred to us. Laboratory work-up revealed secondary adrenal insufficiency and secondary hypothyroidism. Patient was prescribed hydrocortisone and levothyroxine and resulted in significant improvement of the patient’s condition. On the follow up visit patient demonstrated muscle weakness, difficulty getting up from the chair, headache and knee pain, the feeling of numbness variations in blood pressure. Laboratory tests revealed low normal T4 level. The patient was instructed to adjust the dosage of levothyroxine, which resulted in significant clinical improvement.

Conclusion: Central hypothyroidism is a rare and heterogeneous disorder that is characterized by a defect in thyroid hormone secretion in an otherwise normal thyroid gland due to insufficient stimulation by TSH. The disease results from the abnormal function of the pituitary gland, the hypothalamus, or both. Achieving optimal thyroid hormone replacement is more difficult in TSH deficiency compared to primary hypothyroidism because of the inability to be guided by serum TSH levels.A combination of clinical symptoms and free thyroxine levels are typically used to make a diagnosis and monitor replacement.Reference1. Petunina NA, Trukhina LV, Martirosian NS. [Central hypothyroidism]. Ter Arkh. 2019 Oct 15;91(10):135-138. Russian. doi: 10.26442/00403660.2019.10.000358. PMID: 32598643.