LOW TSH LEVELS AND RISK OF CARDIOVASCULAR DISEASE

I HAVE TREATED A NUMBER OF PEOPLE WHO HAVE HAD HYPOTHYROID SYMPTOMS THAT PERSIST EVEN WHEN THEIR TSH LEVELS ARE LOW [< 0.4 mIU/L]. UNDERSTANDABLY, THEIR PRIMARY CARE PHYSICIANS OR ENDOCRINOLOGISTS ARE CONCERNED ABOUT CARDIOVASCULAR DISEASE, SUCH AS ATRIAL FIBRILLATION, AND STROKE OR FRACTURES AS THESE ARE SYMPTOMS OF HYPERTHYROIDISM THAT COULD BE DIAGNOSED BY A LOW TSH. HOWEVER, STUDIES SHOW THAT THE RISK OF THESE PROBLEMS IS GREATER IN OLDER ADULTS, ESPECIALLY IF THEIR TSH IS < 0.03 mU/L

ANOTHER STUDY SHOWED THAT IF THE TSH IS BETWEEN 0.04-0.4 mU/L THERE WAS NOT A GREATER RISK FOR ARRHYTHMIAS OR FRACTURES COMPARED WITH THOSE WITH TSHS IN NORMAL REFERENCE RANGE [0.4-4.4 mIU/L]. HOWEVER, THE RISK INCREASED IF THE TSH WAS LESS THAN 0.03 mU/L. [FLYNN RW, ET AL., SERUM TSH CONCENTRATION AND MORBIDITY FROM CARDIOVASC. DZ AND FRACTURES IN PEOPLE ON LONG TERM LEVOTHYROXINE THERAPY. CLIN ENDOCRINOL METAB 2010; 95:186]

IMPORTANTLY, THERE IS ALSO AN INCREASED CARDIOVASCULAR RISK IF HYPOTHYROIDISM IS UNDER TREATED ALTHOUGH THE TSH IN THE STUDY WAS > 5.5 mU/L.  HOWEVER, IT WAS NOTED THAT A SIMILAR RISK WOULD LIKELY OCCUR FOR SOMEONE WHO HAS A TSH IN THE NORMAL RANGE AND YET WHO HAVE HYPOTHYROIDISM SYMPTOMS.

WHEN LEVOTHYROXINE DOSES WERE HIGH ENOUGH TO LOWER THE TSH TO < 0.3 mU/L. COMBINING T4 AND T3 DID NOT SEEM TO HELP MORE THAN T4 ALONE AND YET WHAT SEEMS TO MAKE A DIFFERENCE IS INCREASING THE LEVOTHYROXINE DOSE SO THE TSH IS < 0.3 mU/L. [ITO M M, ET AL. TSH-SUPPRESSIVE DOSES OF LEVOTHYROXINE ARE REQUIRED TO RAISE T3 TO NORMAL RANGE IN PATIENTS WHO HAVE HAD TOTAL THYROIDECTOMY [WHERE THE PRE THYROIDECTOMY LEVELS MAY BE MORE ACCURATELY NORMAL FOR THE PERSON] AND YET COULD ALSO BE REQUIRED FOR OTHER PATIENTS] EUR J ENDOCRINOL 2012; 167; 373]. POSSIBLY A SLOW RELEASE T3 PRODUCT MAY WORK BETTER BUT IT IS NOT AVAILABLE YET.

COMBINED T4 AND T3 HELPED THE MOST SEVERELY IMPAIRED LOW THYROID PATIENTS. [SHAKIR MKM, ET.AL. COMPARATIVE EFFECTIVENESS OF LEVOTHYROXINE, DESSICATED THYROID EXTRACT, AND LEVOTHYROXINE + LIOTHYRONINE IN HYPOTHYROIDISM. J CLIN ENDOCRINOL METAB 2021; 106:e4400]

ALL OF THIS SHOWS THAT A NORMAL TSH CAN BE 0.03 mU/L, WITH LOW RISK OF CARDIOVASCULAR DISEASE OR LOWERED BONE DENSITY [RISK OF FRACTURES] SIDE-EFFECTS AT THAT TSH LEVEL. ALSO, THE FINDING THAT PEOPLE WITH MORE SYMPTOMS OF LOW THYROID [HYPOTHYROIDISM] BENEFITED FROM COMBINING T4 MEDICATION WITH T3 MEDICATION MAY INDICATE THAT MANY PEOPLE ARE UNDERTREATED WITH T4 RX [LEVOTHYROXINE ALONE.

SO, IF YOU ARE HAVING HYPOTHYROIDISM SYMPTOMS, ALL OF THE ABOVE WOULD SUPPORT INCREASING THE LEVOTHYROXINE DOSE TO SEE IF YOUR SYMPTOMS GO AWAY WITH A POSSIBLE END POINT OF A TSH OF 0.03 mU/L. ASK YOUR PRIMARY CARE PHYSICIAN OR YOUR ENDOCRINOLOGIST ABOUT THIS.