Endocrine Abstracts

95% of all cases of overt hypothyroidism are primary. It is defined as low levels of blood thyroid hormone due to disorder of the thyroid gland causing decreased synthesis and secretion of thyroid hormones. Levothyroxine is recommended as the preparation of choice for the treatment of this disease. The therapy should eliminate the symptoms of hypothyreosis, lead to the normalization of thyroid axis hormones and the avoidance of iatrogenic thyrotoxicosis. Serum TSH is the parameter recommended to monitoring the treatment. The target serum TSH depends on patient age and underlying comorbidities.^{1, 2}. Sometimes, such monitoring may be insufficient. We report the coexistence of primary hypothyroidism and pituitary insufficiency due to pituitary adenoma.

Case report

The patient underwent total thyroidectomy due to giant goiter (histopathological examination excluded neoplasm of thyroid gland) in 2008 year. Postoperative hypothyroidism was treated successfully. The TSH level was stable within limits (1–3 uIU/ml) on levothyroxine dose 150 and 125 µg alternately. In 2018, the TSH level was decreased (TSH <0.05 uIU/ml).The patient was asymptomatic. His weight was unchanged. There were no new medications, supplements or mistakes in levothyroxine treatment. The dose of the drug was reduced to 125 mg. The control results reveled the level of TSH, ft3 and ft4 below the normal range. The patient was admitted to the hospital. The diagnostic test revealed low levels of cortisol, ft4, ft3, testosterone, LH, GH. An MRI scan showed a 34x39x39 mm pituitary adenoma. Unfortunately, ischemic stroke complicated hospitalization, so surgery was delayed. In 2019, the patient underwent transsphenoidal tumor resection. Hydrocortisone and levothyroxine 150 µg were used as replacement therapy. Ft4 levels normalised, TSH level was 0.3 uIU/ml and ft3 remained low due to NTIS.

Conclusions

We should measure ft3 and ft4 during the monitoring of primary hypothyroidism treatment, especially when TSH level declines. TSH levels lowering during the monitoring of primary hypothyroidism treatment may be the marker of concomitant hypopituitarism.

References

1. Pearce SH et al. 2013 ETA Guideline: Management of Subclinical Hypothyroidism. Eur Thyroid J. 2013 Dec;2(4):215–28. doi: 10.1159/000356507.

2. Jonklaas J et al. American Thyroid Association Task Force on Thyroid Hormone Replacement. Guidelines for the treatment of hypothyroidism: prepared by the american thyroid association task force on thyroid hormone replacement. Thyroid. 2014 Dec;24(12):1670–751. doi: 10.1089/thy.2014.0028.